First to second order magnetic phase transformation in la0 7ca0 3 xbaxmno3 exhibiting large magnetocaloric effect

Accepted Manuscript First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect The-Long Phan, N.T Dang, T.A Ho, T.V Manh, T.D Thanh, C.U Jung, B.W Lee, A.T Le, Anh D Phan, S.C Yu PII: S0925-8388(15)31418-3 DOI: 10.1016/j.jallcom.2015.10.162 Reference: JALCOM 35717 To appear in: Journal of Alloys and Compounds Received Date: January 2015 Revised Date: 12 October 2015 Accepted Date: 19 October 2015 Please cite this article as: T.-L Phan, N.T Dang, T.A Ho, T.V Manh, T.D Thanh, C.U Jung, B.W Lee, A.T Le, A.D Phan, S.C Yu, First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect, Journal of Alloys and Compounds (2015), doi: 10.1016/j.jallcom.2015.10.162 This is a PDF file of an unedited manuscript that has been accepted for publication As a service to our customers we are providing this early version of the manuscript The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain ACCEPTED MANUSCRIPT First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect The-Long Phan1,*, N T Dang2, T A Ho3, T V Manh3, T D Thanh4, C U Jung1, B W Lee1, A T Le5, Anh D Phan6, and S C Yu4 Department of Physics and Oxide Research Center, Hankuk University of Foreign Studies, Yongin 449-791, South Korea Institute of Materials Science, Vietnam Academy of Science and Technology, Hoang Quoc Viet, Hanoi, Vietnam Advanced Institute for Science and Technology, Hanoi University of Science and Technology, 01 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam SC Department of Physics, University of Illinois at Urbana-Champaign, Urbana 61801, USA M AN U Institute of Research and Development, Duy Tan University, Da Nang, Vietnam Department of Physics, Chungbuk National University, 361-763 Cheongju, South Korea RI PT Abstract We have prepared polycrystalline samples La0.7Ca0.3-xBaxMnO3 (x = 0, 0.025, 0.05, 0.075 and 0.1) by solid-state reaction, and then studied their magnetic properties and magnetocaloric (MC) effect based on magnetization versus temperature and magnetic-field (M-H-T) measurements Experimental results TE D reveal the easiness in tuning the Curie temperature (TC) from 260 to about 300 K by increasing Badoping concentration (x) from to 0.1 Under an applied field H = 50 kOe, maximum magneticentropy changes around TC of the samples can be tuned in the range between and 11 J⋅kg-1⋅K-1, corresponding to refrigerant-capacity values ranging from 190 to 250 J⋅kg-1 These values are xBaxMnO3 EP comparable to those of some conventional MC materials, and reveal the applicability of La0.7Ca0.3materials in magnetic refrigeration Analyses of the critical behavior based on the Banerjee criteria, Arrott plots and scaling hypothesis for M-H-T data prove a magnetic-phase separation when AC C Ba-doping concentration changes In the doping region x = 0.05-0.075, the samples exhibits the crossover of first- and second-order phase transitions with the values of critical exponents β and γ close to those expected for the tricritical mean-field theory The samples with x < 0.05 and x > 0.075 exhibit first- and second-order transitions, respectively More detailed analyses related to the Griffiths singularity, the critical behavior for different magnetic-field intervals started from 10 kOe, and the magnetic-ordering parameter n = dLn|∆Sm|/dLnH (where ∆Sm is the magnetic-entropy change) demonstrate magnetic inhomogeneities and multicritical phenomena existing in the samples Keywords: Perovskite manganites, Magnetic properties, Critical behavior *Electronic mail: ptlong2512@yahoo.com; Phone: +82-43-261-2269; Fax: +82-43-275-6416 ACCEPTED MANUSCRIPT Introduction Currently, hole-doped perovskite-type manganites with a generally chemical formula of R1xA’xMnO3 (R = La, Pr, Nd; and A’ = Ca, Sr, Ba, Pb) are still attracting intensive interest of the solid- state physics community because they exhibit many intriguing physical phenomena (typically, colossal RI PT magnetoresistance (MR) and magnetocaloric (MC) effects) taking place around magnetic-phase transitions To explain these physical phenomena, theoretical models of exchange interactions [1], polarons (causing Jahn-Teller lattice distortions) [2, 3], and phase separation combined with the SC percolation and Griffiths singularity have been proposed [4-6] It has been agreed with opinions that colossal MR and MC effects in manganites are directly related to ferromagnetic (FM) or M AN U antiferromagnetic (AFM) ordering, charge ordering (CO), and orbital ordering (OO), meaning the interplay of spin, orbital and lattice/phonon degrees of freedom [7] These properties found in R1xA’xMnO3 compounds are dependent on concentration of Mn3+ and Mn4+ ions, which can be easily controlled by changing A’-doping content (x) A coexistence of Mn3+ and Mn4+ ions leads to interaction TE D types known as the FM double-exchange interaction associated with a Mn3+-Mn4+ pair, and the AFM super-exchange interaction associated to Mn3+-Mn3+ and Mn4+-Mn4+ pairs The strength of these interactions is dependent on the structural parameters, such as the bond distance R〈Mn-O〉, the bond angle EP 〈Mn-O-Mn〉, the variance σ2 of ionic radii, and the tolerance factor t = (〈 rA 〉 + rO ) / 2(〈 rB 〉 + rO ) (where 〈rA〉 and 〈rB〉 are average radii of the cations located at A and B sites in the perovskite structure ABO3, AC C respectively, and rO is the radius of oxygen anion), and the effective bandwidth defined as W ∝ cos ω / R〈3.5 Mn − O 〉 , with ω = ( π − 〈 Mn − O − Mn〉 ) [8, 9] Experimental studies have revealed the following phenomena: (i) for Mn3+-rich FM manganites, a decrease of 〈 rA〉 (or t) tends to diminish the 〈 Mn-O-Mn〉 angle, reducing the bandwidth W, and consequently the ferromagnetic-paramagnetic (FMPM) phase-transition temperature (TC, the Curie temperature) [8, 10]; (ii) for Mn4+-rich manganites, a small 〈rA〉 (or t) value is required to result in colossal MR and MC effects [11]; and (iii) at any 〈rA〉 and Mn valence, an increase of σ2 tends to depress FM and AFM interactions, and to destabilize CO [12] ACCEPTED MANUSCRIPT These remarks reveal the complicated relation between the structural parameters and the magnetic and magneto-transport properties of manganites, which is an interesting theme for pure research For La1-xA’xMnO3 compounds, the Mn3+-Mn4+ FM interaction, and colossal MR and MC effects are usually largest when the concentration ratio of Mn3+/Mn4+ is about 7/3, corresponding to an A’- RI PT doping content x ≈ 0.3 Below and above this value, AFM interactions of Mn3+-Mn3+ and Mn4+-Mn4+ pairs are dominant, and thus depress the FM interaction [7, 10] Among La0.7A’0.3MnO3 compounds, La0.7Ca0.3MnO3 has attracted much more interest for both the aspects of pure research and SC technological applications because colossal MR and MC effects together with intriguing physical properties occur near room temperature These properties can be controlled by doping suitable elements M AN U into the sites of La/Ca and/or Mn to change the structural parameters and the Mn3+/Mn4+ ratio Interestingly, the FM-PM phase transition of La0.7Ca0.3MnO3 polycrystalline and single-crystal bulks is followed up with structural changes is discontinuous, which is known as a first-order magnetic phase transition (FOMT) [13-17] For La0.7Ca0.3MnO3 nanoparticles, there is a critical particle size (dc) The TE D nanoparticles with average particle sizes larger than dc exhibit the FOMT [18, 19] Because the width of FM-PM transition region in FOMT materials is narrow, the operating temperature range of CMRbased electronic devices is limited Furthermore, large hysteretic losses of FOMT materials are EP detrimental to the refrigerant capacity (RC, an important parameter used in evaluating a MC material besides the magnetic-entropy change) in refrigeration applications To improve these restrictions, it is AC C necessary to widen the FM-PM transition region upon modifying the FOMT of La0.7Ca0.3MnO3 to a second-order phase transition (SOMT) This process is known as the rounding, where a discontinuous FOMT is rounded to a continuous SOMT by quenched disorder [20, 21] In practice, it can be doped suitable elements into the Mn and/or La/Ca sites [14, 15, 21-24] Another effective route has also been suggested to be the fabrication of low-dimensional La0.7Ca0.3MnO3 materials (thin films and nanoparticles) [13, 18, 19, 25] ACCEPTED MANUSCRIPT To assess the success in rounding a discontinuous FOMT, it can be based on the theory of second-order phase transitions; specifically, Arrott plot methods [26, 27], the scaling hypothesis [21], and Banerjee’s criteria [28] for assessing magnetization isotherms, and/or the universal behavior [2931] for magnetic entropy change Such the works were performed on Sr-, Ba-, Pr-, Ga, Fe-, Co-, Cr-, RI PT and/or Ni-doped La0.7Ca0.3MnO3 compounds [14, 15, 21-24, 32-37] For Ba-doped La0.7Ca0.3MnO3 compounds, though several previous works [15, 38, 39] reported on their magnetic, MC and transport behaviors, detailed analyses related to the FM-PM critical region, magnetic interactions, and SC percolation threshold of the FOMT-SOMT transformation have not been carried out yet Moreover, it has been found that for the manganites exhibiting the crossover of the FOMT and SOMT, and magnetic M AN U inhomogeneity, the values of critical parameters strongly depend on field ranges chosen for analyzing the critical behavior [40, 41] To gain more insight into these problems, we have prepared La0.7Ca0.3xBaxMnO3 compounds, and then investigated in detail their magnetic and MC behaviors The results obtained from analyzing magnetization versus temperature and magnetic-field data reveal all the TE D compounds giving a large MC effect While the samples x = 0.05-0.075 exhibit the crossover of the FOMT and SOMT, those with x < 0.05 and x > 0.075 exhibit the FOMT and SOMT, respectively These results are discussed and compared carefully with previous studies on the same topic EP Experimental details Five perovskite-type manganite samples La0.7Ca0.3-xBaxMnO3 (with x = 0, 0.025, 0.05, 0.075, and AC C 0.1) were prepared from high-purity (99.9 %) precursors La2O3, CaCO3, BaCO3 and MnCO3 in powder (they were purchased from Aldrich, and used as received from commercial sources, without further purification and/or treatment) by using conventional solid-state reaction These precursors combined with stoichiometric masses were well ground and mixed, and then calcinated in air at 1200 oC for 24 hrs After calcinating, the obtained mixtures were re-ground and pressed into pellets under a pressure of about 5000 psi by using a hydraulic press These pellets were finally sintered at 1400 oC for 24 hrs The crystal structure at room temperature of obtained products after sintering was checked by an X-ray ACCEPTED MANUSCRIPT diffractometer (Bruker AXS, D8 Discover) equipped with a Cu-Kα radiation source with wavelength λ =1.5406 Å To minimize errors related to the position calibration of X-ray incident angles, a small amount of standard Si powders was mixed with the samples before recording their X-ray diffraction (XRD) patterns Magnetization measurements versus temperature and magnetic field were performed temperature, with increments of K for M(H) and K for M(T) Results and discussion SC 3.1 Crystal structure analysis RI PT on a superconducting quantum interference device (SQUID) according to the increasing direction of Figure shows room-temperature Miller-indexed XRD patterns of La0.7Ca0.3-xBaxMnO3 samples M AN U with x = 0-0.1 Detailed analyses of the crystal structure based on the card PDF#49-0416 in MDI Jade 5.0 reveal that all the samples crystallized in the orthorhombic structure (space group: Pnma) Though Ba doping with x = 0.025-0.1 does not change the structure type (i.e., no indication of crystal-structure separation), the shift of the XRD peaks towards smaller angles (particularly for the sample x = 0.1, see TE D the inset of Fig 1) demonstrates the change of the lattice parameters (a, b and c) in the doped samples compared with the parent compound La0.7Ca0.3MnO3 Based on the XRD data, we calculated the volume of unit cell (V) from a, b and c As shown in Table 1, V increases from 229.8 to 231.1 Å3 with EP increasing Ba-doping content (x) in La0.7Ca0.3-xBaxMnO3 from to 0.1, respectively This is due to the substitution of Ba2+ with a larger ionic radius (1.35 Å) for Ca2+ (or La3+) with a smaller radius of 1.18 Å AC C (or 1.03 Å) [42] The Ba2+ replacement does not change the Mn3+/Mn4+ content ratio (= 7/3) in the samples, but enhances slightly the values of 〈 rA〉 and t from 1.021 Å and 0.871 for x = to 1.056 Å and 0.884 for x = 0.1, respectively, see Table Increasing Ba-doping content also enhances t towards the value t = of the cubic perovskite (such as SrTiO3), indicating an increase of 〈 Mn-O-Mn〉 towards values closer to 180o [15] Furthermore, with the difference in the electronic structure, the Ba2+ substitution for Ca2+ also causes the difference in the relative intensity of diffraction peaks when Ba concentration increases, see the inset of Fig as an example The results obtained from the structural ACCEPTED MANUSCRIPT analyses are different from those reported by Ulyanov et al on La0.7Ca0.3-xBaxMnO3 [39], where they found the orthorhombic-rhombohedral transformation taking place at a threshold concentration xc = 0.09 Having studied La0.67(Ca1-yBay)0.33MnO3 compounds, Moutis et al found this transformation at y = 0.5 (corresponding to xc ≈ 0.17) [15] Different sample-fabrication conditions could lead to the RI PT phenomena as mentioned above 3.2 Magnetization and susceptibility versus temperature, and the Griffiths phase SC The structural changes influence directly the magnetic and MC properties of the samples Learning about these problems, we have investigated temperature and magnetic-field dependences of M AN U magnetization, M(T, H) Figure 2(a) shows field-cooled M(T) data normalized to the M values at K for La0.7Ca0.3-xBaxMnO3 samples in the field H = 100 Oe The results reveal that M values at temperatures below 250 K for x = 0-0.075 and 280 K for x = 0.1 are quite stable Increasing temperature above these values leads to a rapid decrease of M because of the FM-PM transition, where TE D FM coupling of magnetic moments is collapsed by thermal energy By plotting the dM/dT versus T curves, their minima indicate the FM-PM transition temperature (TC, the Curie temperature) of the samples As shown in Figure 2(b) and Table 1, the TC values are about 260 K for x = and 0.025, and EP 267, 268 and 300 K for x = 0.05, 0.075 and 0.1, respectively The increase of TC with increasing Badoping content in La0.7Ca0.3-xBaxMnO3 is in good agreement with the previous reports [15, 38, 39], and AC C related to the increase of 〈rA〉 and t, as mentioned in the introduction part Carefully reviewing previous studies on doped La0.7Ca0.3MnO3 compounds, it can be found that the replacement of Ca2+/La3+ by Ba2+, Sr2+ or Pb2+ usually increases TC [14, 15, 23, 43, 44] A similar situation is also found in La0.7Ca0.3MnO3 compounds doped with Ag+, Na+ or K+ [45-47] In contrast, the replacements of Ca2+/La3+ by Pr3+ and Cd2+ [36, 48-50], and of Mn by a transition metal (Co, Fe, Ni, Ti, Cr, Cu, Ga or Al) [21, 22, 24, 33, 35, 37, 51-53] decrease Tc remarkably These results are tightly related to the ACCEPTED MANUSCRIPT changes of the structural parameters and/or Mn3+/Mn4+ content ratio, which change the bandwidth W of perovskite manganites [7-9, 54, 55] From the M(T) data, performing χ-1(T) = H/M(T) curves (see Figure 3) reveals their linear variation at temperatures above the so-called Griffiths temperature (TG) [6], corresponding to xBaxMnO3 RI PT temperature points indicated by the arrows in Figure and its inset; TG values of the samples La0.7Ca0.3are also listed in Table In this temperature range (T > TG), the samples exhibit the Curie- Weiss (CW) PM behavior; i.e., the magnetic susceptibility (χ-) versus temperature obeys a function SC χ(T) = C/(T-θ), where C and θ are the Curie constant and CW temperature, respectively Fitting the linear χ-1(T) data to the CW law introduces C and θ values Using the relation C = N(µBPeff)2/3kB, with M AN U the number of ions N = 6.023×1023 mol-1, the Bolzmann constant kB = 1.3806×10-23 J/K and the Bohr magneton µB = 9.274×10-24 J/T, we obtained the effective PM moment (Peff) The values θ and Peff of the samples are shown Table It is known that for La0.7Ca0.3-xBaxMnO3 compounds in the PM region, there is the contribution of free magnetic moments of Mn3+ (Peff = 4.9µB) and Mn4+ (Peff = 3.9µB) ions TE D to the PM susceptibility, Peff = for La3+ [56] Because the Mn3+/Mn4+ content ratio (= 7/3) in the samples is unchanged by the Ba doping, the effective moment calculated from the equation 2 is thus 4.6µB This value is about 1.2-1.5 times smaller than the Peff values Peff2 = 0.3µ Mn 4+ + 0.7 µ Mn3+ EP determined from fitting the χ-1(T) data to the CW law (see Table 1), suggesting the formation of FM AC C clusters of Mn3+-Mn4+ double-exchange pairs in the PM region [57] Particularly, below TG there is a downturn in the χ-1(T) curves before TC is reached This is an indication of the Griffiths transition [4, 6], characterized by a susceptibility exponent χ −1 ∝ (T − TCrand )1−λ , where TCrand is the random transition temperature, and λ (≤ 1) is a non-universal positive exponent Fitting the χ-1(T) data above TC to this equation determined simultaneously the values of TCrand and λ As shown in Table 1, the TCrand values of the samples are higher than TC, proving the formation of complex FM/anti-FM states at temperatures between TC and TCrand In the Griffith ACCEPTED MANUSCRIPT phase region between TCrand and TG, there is a random distribution of FM clusters within the globally PM phase [6] For the parent compound La0.7Ca0.3MnO3 exhibiting simultaneously the FOMT and Griffiths singularity [4, 6], its CW temperature θ = 256 K is a little bit smaller than TC = 260 K However, a similar circumstance did not happen for the Ba-doped samples because their magnetic- RI PT phase feature was changed, as being further confirmed below For the exponent λ, its value gradually decreases from 0.22 to 0.11 when x in La0.7Ca0.3-xBaxMnO3 increases from to 0.1, respectively, see Table 1, proving the suppression of the Griffiths phase At high applied fields, it has been observed the SC suppression of the Griffiths phase [5, 58, 59] In fact, the Griffiths phase was found popularly in some manganites and cobaltites; for examples, La1-x(Ca, Ba, Sr, Pb)xMnO3 [4, 6, 60, 61], (Nd1-xYx)0.7- M AN U Sr0.3MnO3 [62, 63], Sm1-x(Ca, Sr)xMnO3 [5, 58, 64], and La0.6Sr0.4Mn1–xCoxO3 [65] For compounds with the presence the Griffiths phase, their magnetic properties versus temperature can be divided into the following characteristic regions: (i) T ≤ TC, (ii) TC ≤ T ≤ TCrand , (iii) TCrand ≤ T ≤ TG, and (iv) T > TG FM order is considered to be gradually decreases with increasing temperature from (i) to (iv) In TE D normally inhomogeneous ferromagnets, the values of TCrand and TC are close to each other, and thus the regions (i) and (ii) are almost the same [61] For ferromagnets with a higher inhomogeneity (like the case of our samples, and those shown in Refs [4, 65]), all the regions (i)-(iv) would be apparent EP 3.3 Magnetic phase transition and critical behavior AC C To get more insight into the phase-transition type, magnetic interactions and MC effect of the samples La0.7Ca0.3-xBaxMnO3, we have recorded M(H) data at different temperatures around the FMPM transition These M(H) data are then performed as H/M versus M2, and graphed in Figure 4, which are defined as the inverse Arrott plots [26] For x = 0, in the vicinity of TC, its M(H) curves have the Slike shape, and the slopes of H/M versus M2 curves at low fields are negative, Figures 4(a, b) These features disappear gradually when x in La0.7Ca0.3-xBaxMnO3 increases from 0.025 to 0.05, Figures 4(cf) For higher x values (= 0.075 and 0.1), positive slopes and no S shape are observed, Figures 4(g-j) According to Banerjee’s criteria [28], a positive or negative slope indicates the FOMT or SOMT, ACCEPTED MANUSCRIPT respectively With these features, we can precariously conclude that the samples with x = 0, 0.025 and 0.05 exhibit the FOMT characterization while those with x = 0.075 and 0.1 exhibit the SOMT characterization In the range x = 0.05-0.075, La0.7Ca0.3-xBaxMnO3 compounds seem exhibit the crossover of the FOMT-SOMT transformation To further clarify these preliminary judgments, it RI PT should be better to determine the critical exponents β, γ, and δ associated with temperature dependences of the spontaneous magnetization, Ms(T), inverse initial susceptibility, χ 0−1 (T), and critical isotherm, M(H) at TC, respectively In method, these exponents can be determined by using the SC modified Arrott plot (MAP) method [27] Firstly, we suppose that all the samples La0.7Ca0.3-xBaxMnO3 relations [21, 66] Ms(T) = M0(-ε)β, χ 0−1 (T) = (h0/M0)εγ, M(H, TC) = DH1/δ, M AN U undergoing the SOMT Variations of Ms(T), χ0-1(T) and M(H, TC) data around TC thus obey asymptotic ε < 0, (1) ε > 0, (2) ε =0, (3) TE D where M0, h0 and D are critical amplitudes, and ε = (T-TC)/TC is the reduced temperature According to the MAP method, the values of critical parameters TC, β andγ are determined from the Arrott-Noakes equation of state (H/M)1/γ = aε + bM1/β, where a and b are temperature-dependent parameters [21] EP This equation implies that with correct β and γ values the performance of M1/β versus (H/M)1/γ curves in AC C the vicinity of TC introduces parallel straight lines, and one of these lines passes through the coordinate origin at TC According to the mean-field (MF) theory proposed for ferromagnets exhibiting long-range magnetic interactions, β and γ values are 0.5 and 1.0, respectively [67] The plot of M1/β versus (H/M)1/γ curves with β = 0.5 and γ = 1.0 (corresponding to normal Arrott plots of M2 versus H/M) [26] does not introduce parallel straight lines as mentioned, see Figure This demonstrates that the MF exponents are unsuitable to describe magnetic interactions in the samples La0.7Ca0.3-xBaxMnO3 In other words, ACCEPTED MANUSCRIPT Rhombohedral 357 0.45±0.01 1.2 3.67 [82] La0.7Sr0.3MnO3 (PC) Rhombohedral 360 0.387±0.008 1.166±0.014 4.01 [52] La0.7Sr0.3MnO3 (TF) Rhombohedral 361 0.45±0.02 1.08±0.04 3.4 [85] La0.7Sr0.3Mn0.94Co0.06O3 (PC) Rhombohedral 311 0.478±0.013 1.165±0.027 3.44 [52] La0.7Sr0.3Mn0.92Co0.08O3 (PC) Rhombohedral 297 0.483±0.018 1.112±0.028 3.30 [52] La0.7Sr0.3Mn0.9Co0.1O3 (PC) Rhombohedral 281 0.487±0.016 1.109±0.063 3.28 [52] La0.75Sr0.25MnO3 (SC) Rhombohedral 346 0.40±0.02 1.27±0.06 4.12±0.33 [125] La0.8Sr0.2MnO3 (PC) Rhombohedral 316 0.50±0.02 1.08±0.03 3.13±0.2 [73] La0.8Sr0.2MnO3 (SC) Rhombohedral 305 0.45±0.05 - - [126] La0.875Sr0.125MnO3 (SC) Rhombohedral 186 0.37±0.02 1.38±0.03 4.72±0.04 [127] La0.7Sr0.3Mn0.95Ti0.05O3 (PC) Rhombohedral 304 0.344 1.149 4.340 [83] La0.7Sr0.3Mn0.92Ti0.08O3 (PC) Rhombohedral 235 0.425±0.016 1.017±0.055 3.39±0.04 [128] La0.7Sr0.3Mn0.99Ni0.01O3 (PC) Rhombohedral La0.7Sr0.3Mn0.98Ni0.02O3 (PC) Rhombohedral La0.7Sr0.3Mn0.97Ni0.03O3 (PC) Rhombohedral La0.7Sr0.3Mn0.95Al0.05O3 (PC) Rhombohedral La0.67Sr0.33Mn0.99Mo0.01O3 (PC) Rhombohedral La0.67Sr0.33Mn0.98Mo0.02O3 (PC) La0.67Sr0.33Mn0.96Mo0.04O3 (PC) 0.394±0.015 1.092±0.047 3.99±0.05 [129] 353 0.444±0.017 1.081±0.032 3.79±0.08 [129] 343 0.468±0.006 1.010±0.021 2.67±0.06 [129] 336 0.458 1.001 3.185 [83] 368 0.39±0.01 1.17±0.01 4.0±0.1 [123] Rhombohedral 367 0.40±0.01 1.15±0.01 3.9±0.1 [123] Rhombohedral 366 0.35±0.01 1.25±0.01 4.6±0.1 [123] Rhombohedral 365 0.41±0.01 1.13±0.01 3.8±0.1 [123] Rhombohedral 361 0.39±0.01 1.17±0.01 4.0±0.1 [123] EP La0.67Sr0.33Mn0.94Mo0.06O3 (PC) SC M AN U 357 TE D La0.67Sr0.33Mn0.97Mo0.03O3 (PC) RI PT La0.7Sr0.3MnO3 (PC) La0.6Sr0.4Mn0.8Fe0.1Cr0.1O3 (PC) Rhombohedral 212 0.395±0.010, 1.402±0.010 5.208±0.007 [130] LaMn0.95Ti0.05O3 (PC) Rhombohedral 173 0.378±0.007 1.29±0.02 4.19±0.03 [131] Rhombohedral 145 0.375±0.005 1.25±0.02 4.11±0.04 [131] LaMn0.85Ti0.15O3 (PC) Rhombohedral 122 0.376±0.003 1.24±0.01 4.16±0.03 [131] LaMn0.8Ti0.2O3 (PC) Rhombohedral 95 0.359±0.004 1.28±0.01 4.21±0.05 [131] LaMn0.9Fe0.1O3 (PC) Rhombohedral 136 0.358 ± 0.007 1.328 ± 0.003 4.71 ± 0.06 [132] La0.79Sr0.21CoO3 (SC) Rhombohedral 188 0.491±0.004 1.217±0.003 3.51±0.01 [71] La0.75Sr0.25CoO3 (SC) Rhombohedral 214 0.362±0.002 1.304±0.006 4.75±0.01 [71] La0.5Sr0.5CoO3 (PC) Rhombohedral 223 0.321±0.002 1.351±0.009 4.39±0.02 [66] La0.8Sr0.2CoO3 (PC) Rhombohedral 199 0.46 1.39 4.02 [74] AC C LaMn0.9Ti0.1O3 (PC) 36 ACCEPTED MANUSCRIPT Rhombohedral 222 0.46 1.39 4.02 [74] La0.7Sr0.3CoO3 (PC) Rhombohedral 223 0.43 1.43 4.38 [74] La0.67Pb0.33Mn0.92Co0.08O3 (PC) Rhombohedral 316 0.364±0.002 1.40±0.112 4.88±0.01 [80] La0.6Nd0.1(CaSr)0.3Mn0.9V0.1O3 (PC) Rhombohedral 298 0.385±0.001 1.481±0.003 4.672±0.002 [133] La0.57Nd0.1Pb0.33MnO3 (PC) Rhombohedral 350 0.371 1.380 4.270 [134] La0.57Nd0.1Sr0.33MnO3 (PC) Rhombohedral 352 0.356±0.009 1.152±0.016 4.235 [135] La0.57Nd0.1Sr0.305MnO3 (PC) Rhombohedral 350 0.320±0.005 La0.57Nd0.1Sr0.28MnO3 (PC) Rhombohedral 349 0.312 La0.57Nd0.1Sr0.33MnO3 (PC) Rhombohedral 341 0.326±0.007 La0.57Nd0.1Sr0.33Mn0.95Al0.05O3 (PC) Rhombohedral 300 0.344±0.002 La0.57Nd0.1Sr0.33Mn0.9Al0.1O3 (PC) Rhombohedral 288 0.352±0.008 La0.57Nd0.1Pb0.33Mn0.95Ti0.05O3 (PC) Rhombohedral 321 0.391 La0.8Na0.1MnO3 (PC) Rhombohedral LaMnO3.14 (PC) Rhombohedral La0.9Pb0.1MnO3 (PC) Pseudo- [135] 1.173±0.004 4.760 [135] 1.329±0.001 5.07 [136] 1.332±0.004 4.87 [136] 1.342±0.002 4.81 [136] 1.276 4.466 [134] 1.083 3.18 [89] 141 0.415 1.470 4.542 [137] 162 0.498 1.456 3.92 [88] 291 0.499 1.241 3.49 [88] TE D M AN U SC 4.753 0.495 346 0.502 1.063 3.12 [88] Monoclinic 240 0.387±0.006 0.884±0.002 3.284±0.003 [138] Monoclinic 160 0.516±0.008 0.993±0.006 3.046±0.002 [138] Tetragonal 242 0.5217 1.209 3.162 [139] Tetragonal 109 0.372±0.004 1.347±0.001 4.67±0.03 [140] Pseudorhombohedral La0.7Pb0.3MnO3 (PC) 1.201±0.002 295 rhombohedral La0.8Pb0.2MnO3 (PC) RI PT La0.75Sr0.25CoO3 (PC) Pseudo- Pr0.5Sr0.5CoO3 (PC) Pr0.5Sr0.5CoO2.83 (PC) La0.4Bi0.3Sr0.3MnO3 (PC) AC C Nd0.85Pb0.15MnO3 (SC) EP rhombohedral Nd0.7Pb0.3MnO3 (SC) Tetragonal 149 0.361±0.013 1.325±0.001 4.62±0.04 [140] Nd0.6Pb0.4MnO3 (SC) Cubic 156 0.329±0.006 1.329±0.003 4.54±0.10 [141] Nd0.67Sr0.33MnO3 (PC) Pseudo-cubic 227 0.23±0.02 1.05±0.03 0.513±0.04 [75] Pr0.77Pb0.33MnO3 (SC) Pseudo-cubic 167 0.344±0.001 1.352±0.006 4.69±0.02 [142] Pr0.7Pb0.3MnO3 (SC) Pseudo-cubic 197 0.404±0.001 1.357±0.006 4.37±0.09 [142] Pr0.8Pb0.2MnO3 (PC) Pseudo-cubic 204 0.468±0.004 1.353±0.083 3.78±0.02 [143] Pr0.9Pb0.1MnO3 (PC) Pseudo-cubic 151 0.443±0.027 1.337±0.042 3.99±0.07 [143] *Note: The critical behavior with different magnetic-field ranges 37 ACCEPTED MANUSCRIPT Table Experimental values of TC (determined from the M(T)|H=100 Oe data), and MC-related parameters (-∆Smax, RC, and RCP) for our La0.7Ca0.3-xBaxMnO3 samples compared with those for Gd and typical manganites exhibiting the giant MC effect, with magnetic-field variations up to 50 kOe Gd 295 La0.7Ca0.3MnO3 (PC) 260 La0.7Ca0.275Ba0.025MnO3 (PC) 260 La0.7Ca0.25Ba0.05MnO3 (PC) 267 La0.7Ca0.225Ba0.075MnO3 (PC) La0.7Ca0.2Ba0.1MnO3 (PC) 300 La0.7Ca0.3MnO3 (PC) 264 La0.7Ca0.3MnO3 (PC) -1 RCP ( J⋅kg ⋅K ) ( J⋅kg-1 ) 20 6.1 240 - 50 10.6 820 - 20 7.8 92 124 50 10.7 247 278 20 6.4 85 109 50 9.2 235 276 20 6.3 79 101 50 9.1 230 267 20 4.1 70 90 50 7.1 190 241 -1 Ref [29] This work This work This work This work 20 3.1 79 105 This work 50 6.0 210 246 50 7.7 ~187 - [13] 20 8.0 - - [99] 50 9.9 - - 50 4.9 ~150 - [13] La0.7Ca0.3MnO3 (NPs) 260 La0.7Ca0.3MnO3 (NPs) 235-270 45 5.0-8.6 - 218-243 [25] La0.7Ca0.3MnO3 (TFs) TE D 242 (kOe) RC ( J⋅kg ) -1 M AN U 268 -∆Smax RI PT (K) ∆H SC TC Material 235 50 ~2.5 200 - [13] 275 50 10.5 - 462 [97, 98] 308 50 7.5 - 374 [97, 98] 340 50 7.0 - 369 [97, 98] 341 50 6.9 - 364 [97, 98] 284 30 4.3 116 150 [40] 100~240 20 1.3~8.0 - 100~160 [49] 50 5.4~8.2 197~259 - [36, 48] 50 8.5 - 511 [97] 20 5.3 80 94 [62] 50 8.3 205 259 20 4.1 102 127 50 7.2 245 288 83-375 50 3.2-4.5 180-257 - [101] La0.7Ca0.25Sr0.05MnO3 (SC) La0.7Ca0.2Sr0.1MnO3 (SC) La0.7Ca0.1Sr0.2MnO3 (SC) La0.7Ca0.05Sr0.25MnO3 (SC) EP La0.7Ca0.2Sr0.1MnO3 (PC) La0.7-xPrxCa0.3MnO3 (x = 0-0.69) (PC) La0.7-xPrxCa0.3MnO3 (x = 0-0.45) (PC) AC C Pr0.63Sr0.37MnO3 (SC) Nd0.7Sr0.3MnO3 (PC) (Nd0.93Y0.07)0.7Sr0.3MnO3 (PC) Sm0.7-xLaxSr0.3MnO3 (x = 0-0.7) (PC) Sm1-xSrxMnO3 (x = 0.42-0.46) (PC) 305 240 175 [62] 130-134 50 4.6 178-182 - [100] Sm0.58Sr0.42MnO3 (PC) 135 50 9.3 302 362 [96] Sm0.58Sr0.42MnO3 (NPs) 135 50 5.9 208 253 [96] 38 x=0 x = 0.025 x = 0.075 x = 0.1 (121) 32.2 32.4 RI PT TE D 30 AC C EP 20 40 2θ (degree) Fig Phan et al 39 Si (321) (103) (222) Si (042) 32.8 SC (040) 32.6 M AN U Si (202) (022) (020) Intensity (arb units) 32.0 (200) (220) (200) (121) ACCEPTED MANUSCRIPT x = 0.1 x = 0.075 x = 0.05 x = 0.025 x=0 50 60 ACCEPTED MANUSCRIPT (a) 0.6 H = 100 Oe 0.4 0.2 0.0 100 150 (b) EP AC C dM/dT -0.5 200 250 TE D 0.0 SC x=0 x = 0.025 x = 0.05 x = 0.075 x = 0.1 M AN U M/MT = 5K 0.8 -1.0 RI PT 1.0 350 268 K x=0 x = 0.05 x = 0.075 x = 0.1 300 K 267 K -1.5 100 300 260 K 150 200 250 T (K) Fig Phan et al 40 300 350 SC 320 K 500 2000 255 270 M AN U -1 χ (Oe.g/emu) 275 K 1000 285 300 T (K) 315 K TE D −1 χ (Oe.g/emu) x = 0.025 x = 0.05 x = 0.075 x = 0.1 x=0 1500 3000 RI PT ACCEPTED MANUSCRIPT 304 K EP 1000 330 K AC C 260 280 300 T (K) Fig Phan et al 41 320 340 ACCEPTED MANUSCRIPT (a) (b) 233 K 1200 x=0 271 K 60 233 K 271 K 30 x=0 15 30 45 (c) 60 2000 (d) 220 K 4000 SC 220 K 280 K 30 M (emu/g) 90 30 45 (e) M AN U x = 0.025 15 60 2500 (f) 244 K 60 5000 282 K 7500 1200 800 400 1200 x = 0.05 800 244 K 282 K 30 8000 6000 x = 0.025 280 K 60 0 RI PT 400 0 90 800 400 x = 0.05 15 (g) 45 60 250 K 60 2000 (h) 4000 296 K 6000 x = 0.075 250 K 1500 1000 296 K 500 EP 30 x = 0.075 15 30 45 AC C 0 30 TE D 0 (i) 60 260 K 2000 (j) 4000 314 K 6000 x = 0.1 1200 60 260 K 800 320 K 30 400 x = 0.1 0 15 30 45 60 H (kOe) 2000 4000 2 M (emu/g) Fig Phan et al 42 6000 H/M (Oe.g/emu) 90 ACCEPTED MANUSCRIPT x10 x10 x10 21 (a) 235 K β = 0.365 γ = 1.336 x=0 (f) 75 235 K β = 0.325 γ = 1.241 x=0 14 0 50 100 150 x10 β = 0.365 γ = 1.336 220 K 300 0 50 100 150 β = 0.325 γ = 1.241 220 K 10 0 80 (h) 60 20 160 240 0 50 100 150 0 200 4 x10 x10 x = 0.075 12 β = 0.365 250 K γ = 1.336 x = 0.05 252 K 70 140 β = 0.325 γ = 1.241 210 280 54 (i) x = 0.075 250 K β = 0.325 γ = 1.241 276 K 60 x = 0.1 280 K β = 0.365 γ = 1.336 AC C 10 (e) 0 180 0 80 160 50 100 150 200 250 β = 0.25 γ=1 400 800 1200 x10 (m) 30 x = 0.05 β = 0.25 γ=1 252 K 20 10 280 K 0 300 600 900 1200 30 (n) x = 0.075 250 K β = 0.25 γ=1 10 276 K 300 600 900 1200 x10 40 (j) 30 x = 0.1 280 K β = 0.325 γ = 1.241 20 (o) x = 0.1 280 K 15 β = 0.25 γ=1 10 10 0 280 K 20 316 K 0 320 240 x10 x10 120 276 K 18 EP 0 220 K 20 36 1200 x10 TE D (d) 320 280 K M 280 K x = 0.025 280 K 40 54 (l) M AN U β = 0.365 γ = 1.336 x = 0.05 252 K 900 18 30 x10 15 (c) 600 36 x10 300 x10 90 (g) x = 0.025 200 0 SC 280 K 271 K 60 1/β 200 x10 x = 0.025 14 (emu/g) 100 21 (b) 1/β 0 200 15 271 K 25 RI PT 271 K β = 0.25 γ=1 30 50 235 K x=0 (k) 45 316 K 80 160 240 1/γ 320 1/γ (H/M) (Oe.g/emu) Fig Phan et al 43 400 00 316 K 400 800 1200 1600 ACCEPTED MANUSCRIPT 55 (a) -1 χ0 β = 0.216 ±0.005 250 γ = 0.973 ±0.069 255 260 265 TC = 292.5 TC = 292.6 TC = 257.8 γ = 1.382±0.012 β = 0.301±0.001 15 280 270 285 290 600 50 Ms -1 χ0 250 260 265 270 275 γ = 0.982 ±0.015 255 15 280 400 χ0 -1 TE D 200 TC = 261.7 TC = 261.5 β = 0.238 ±0.005 255 60 γ = 1.016 ±0.008 30 290 295 300 305 310 30 β = 0.253 ±0.001 15 250 255 260 265 x = 0.1 300 TC = 293.8 TC = 293.9 β = 0.322±0.001 280 285 γ = 1.381±0.031 290 295 300 305 310 600 (h) 450 45 χ0 360 x = 0.1 Ms -1 H = 40-50 kOe TC = 264.2 450 (g) H = 30-40 kOe (d) x = 0.075 45 150 260 265 270 275 EP 250 285 45 x = 0.075 H = 30-40 kOe 40 γ = 1.380±0.008 600 (c) 50 TC = 292.6 β = 0.312±0.002 Ms 245 150 TC = 292.7 TC = 259.1 β = 0.224 ±0.008 200 30 300 H = 20-30 kOe M AN U 30 TC = 258.8 AC C Ms (emu/g) 40 450 x = 0.1 400 H = 20-30 kOe 305 (f) 45 x = 0.075 300 SC (b) 295 -1 35 150 150 30 40 TC = 257.8 H = 10-20 kOe Ms H = 10-20 kOe 45 300 x = 0.1 H = 40-50 kOe 240 300 30 120 γ = 0.992 ±0.002 270 TC = 294.4 150 TC = 264.1 15 275 TC = 294.5 β = 0.326±0.005 γ = 1.342±0.015 280 285 290 295 T (K) 300 T (K) Fig Phan et al 44 χ0 (Oe.g/emu) x = 0.075 RI PT 50 (e) 45 300 305 310 ACCEPTED MANUSCRIPT (b) T < TC 100 x = 0.1 T < TC β = 0.216 γ = 0.973 200 (c) 10 (d) x = 0.1 T < TC T < TC M AN U β = 0.224 γ = 0.982 TC = 258.9 T > TC 10 10 200 (e) T > TC 7 10 x = 0.075 TE D T < TC β = 0.238 γ = 1.016 100 T > TC T > TC 100 10 10 300 200 100 10 300 x = 0.1 (h) 200 T < TC β = 0.326 γ = 1.342 β = 0.253 γ = 0.992 TC = 264.1 T > TC 10 100 TC = 292.6 EP T < TC β = 0.312 γ = 1.380 10 x = 0.075 200 TC = 293.8 T > TC 10 (g) 300 β = 0.322 γ = 1.381 10 200 TC = 261.6 10 x = 0.1 (f) T < TC AC C β M/|ε| (emu/g) 10 10 x = 0.075 100 TC = 292.5 T > TC SC 10 100 β = 0.301 γ = 1.382 TC = 257.8 T > TC 300 200 β+γ H/|ε| 10 (Oe) Fig Phan et al 45 TC = 294.4 10 100 β (a) x = 0.075 RI PT 200 T = 276-310 K M/|ε| (emu/g) T = 250-274 K ACCEPTED MANUSCRIPT 12 (a) x=0 50 kOe RI PT 10 kOe 240 250 260 270 280 (b) x = 0.025 50 kOe 10 kOe 255 270 285 M AN U 240 x = 0.05 (c) 50 kOe 10 kOe 250 260 TE D -1 -1 −∆Sm (J.kg K ) 225 SC 270 (d) EP 260 280 50 kOe 10 kOe 270 280 290 300 x = 0.1 (e) 50 kOe 255 290 x = 0.075 AC C 250 290 10 kOe 270 285 300 T (K) Fig Phan et al 46 315 330 ACCEPTED MANUSCRIPT 12 (a) La0.7Ca0.3-xBaxMnO3 x=0 (n = 0.43) RI PT x=0.05 (n = 0.45) -1 -1 |∆Smax| (J.kg K ) x=0.025 (n = 0.45) x=0.075 (n = 0.64) x=0.1 (n = 0.73) SC 15 30 (b) 45 60 x= x = 0.025 x = 0.05 x = 0.075 x = 0.1 TE D 240 160 AC C EP RC (J/kg) M AN U 0 80 n |∆Smax| ~ H 0 15 30 H (kOe) Fig Phan et al 47 45 ACCEPTED MANUSCRIPT (a) x=0 10 kOe 20 kOe 30 kOe 40 kOe 50 kOe 240 250 (b) 260 270 10 kOe 20 kOe 30 kOe 40 kOe 50 kOe 240 (c) 260 (d) AC C 250 270 TE D 250 285 (e) 10 kOe 20 kOe 30 kOe 40 kOe 50 kOe 280 x = 0.075 EP 270 x = 0.05 255 M AN U n(T, H) 225 SC 280 x = 0.025 RI PT 260 270 10 kOe 20 kOe 30 kOe 40 kOe 50 kOe 280 290 300 x = 0.1 10 kOe 20 kOe 30 kOe 40 kOe 50 kOe 270 285 300 T (K) Fig 10 Phan et al 48 315 330 ACCEPTED MANUSCRIPT 0.8 (a) x=0 0.0 -4 0.8 -2 (b) (c) 0.4 0.0 -4 x =0.05 -2 x = 0.075 (d) TE D 0.8 SC -2 M AN U ∆S' 0.8 x = 0.025 0.4 0.0 -4 RI PT 0.4 0.4 EP 0.0 -4 AC C 0.8 -2 x= 0.1 (e) 0.4 0.0 -4 -2 θ2 Fig 11 Phan et al 49 ACCEPTED MANUSCRIPT Highlights • Threshold of first-to-second-order phase transformation in La0.7Ca0.3-xBaxMnO3 • Giant magneto-caloric effect with magnetic-entropy changes of 6~11 J⋅kg-1⋅K-1 • Detailed analyses of critical behavior in comparison with previous studies AC C EP TE D M AN U SC RI PT • Magnetic phase-transition theories and universal curves of magnetic-entropy change ...ACCEPTED MANUSCRIPT First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect The-Long Phan1,*, N T Dang2, T A Ho3,... shown in Table 1, V increases from 229.8 to 231.1 Å3 with EP increasing Ba-doping content (x) in La0.7Ca0.3-xBaxMnO3 from to 0.1, respectively This is due to the substitution of Ba2+ with a larger... M1/β versus (H/M)1/γ curves in AC C the vicinity of TC introduces parallel straight lines, and one of these lines passes through the coordinate origin at TC According to the mean-field (MF) theory