Magnetocaloric effect and critical behavior in Fe-La-Zr rapidly quenched ribbons

A thorough analysis on critical exponents around the ferromagnetic-paramagnetic phase transition, using the ArrotteNoakes plots and KouveleFisher method, sheds light on the critical magnetic behavior and its association with the magnetocaloric effect in the Fe-La based alloys.

Journal of Science: Advanced Materials and Devices (2018) 406e411 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Magnetocaloric effect and critical behavior in Fe-La-Zr rapidly quenched ribbons Kieu Xuan Hau a, b, *, Nguyen Hoang Ha c, d, Nguyen Le Thi b, c, Nguyen Hai Yen a, d, Pham Thi Thanh a, d, Pham Duc Huyen Yen b, e, Nguyen Huy Ngoc a, Tran Dang Thanh a, d, Victor V Koledov f, Dong Hyun Kim b, Seong-Cho Yu b, **, Nguyen Huy Dan a, d a Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Ha Noi, Viet Nam Chungbuk National University, Cheongju 361 - 763, South Korea Hong Duc University, 565 Quang Trung, Dong Ve, Thanh Hoa, Viet Nam d Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Ha Noi, Viet Nam e VNU University of Engineering and Technology, 144 Xuan Thuy, Ha Noi, Viet Nam f Kotelnikov Institute of Radio-engineering and Electronics of RAS, Moscow, Russia b c a r t i c l e i n f o a b s t r a c t Article history: Received 11 May 2018 Received in revised form 28 October 2018 Accepted November 2018 Available online 14 November 2018 Fe90-xLaxZr10 (x ¼ and 2) rapidly quenched ribbons with thickness of about 15 mm were prepared by the melt-spinning method X-ray diffraction analysis shows that the structure of the ribbons is mostly amorphous The Curie temperature, TC, of the alloy considerably increased, from ~262 K for x ¼ to ~302 K for x ¼ 2, with increasing La-concentration The maximum magnetic entropy change, jDSmjmax, of the alloy is about 1.1 J∙kgÀ1KÀ1 for a magnetic field change DH ¼ 12 kOe A quite large refrigerant capacity (RC ~ 74 J∙kgÀ1 for DH ¼ 12 kOe) near the room temperature region is obtained for the alloy A thorough analysis on critical exponents around the ferromagnetic-paramagnetic phase transition, using the ArrotteNoakes plots and KouveleFisher method, sheds light on the critical magnetic behavior and its association with the magnetocaloric effect in the Fe-La based alloys © 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Magnetocaloric effect Magnetic refrigerant Critical parameter Magnetic entropy change Melt-spinning method Introduction In recent years, an emerging refrigeration technology based on the magnetocaloric effect (MCE) has been attracting many scientists and engineers The MCE is known to be due to an adiabatic temperature change (DTad) or an isothermal magnetic entropy change (DSm) in a magnetic material when it is magnetized or demagnetized In comparison with the conventional gascompression refrigeration, magnetic refrigeration is more environmentally friendly and energetically efficient Currently, it is necessary to find magnetocaloric materials with large values of DSm and refrigerant capacity (RC) in the room temperature region * Corresponding author Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Ha Noi, Viet Nam ** Corresponding author Chungbuk National University, 28644, South Korea E-mail addresses: kieuxuanhau0106@gmail.com (K.X Hau), scyu@chungbuk.ac kr (S.-C Yu) Peer review under responsibility of Vietnam National University, Hanoi Up to now, a large number of magnetic materials possessing large MCEs have been discovered, such as Gd-containing alloys, Ascontaining alloys, La-containing alloys, Heusler alloys, amorphous alloys, and ferromagnetic perovskite maganites [1,2] The materials (for example: As-containing alloys, La-containing alloys, Heusler alloys), which undergo a first-order phase transition (FOPT), have a large magnetic entropy change However, the large MCE of these alloys only occurs in a narrow temperature range due to the nature of the FOPT Thus, the practical application of FOPT materials in magnetic refrigeration is quite limited [3e5] On the other hand, materials such as amorphous alloys, Gd-containing alloys, rareearth intermetallic compounds having a second-order magnetic phase transition (SOPT) exhibit a moderate magnetic entropy change, but its temperature distribution spans over a wide temperature range [6e8] Such a typical example of magnetocaloric materials is amorphous alloys Among the amorphous alloys, Fe-Zr based rapidly quenched alloys are of particular interest as they possess the giant magnetocaloric effect (GMCE), with broad DSm peaks around the Curie temperatures, low coercivity, high https://doi.org/10.1016/j.jsamd.2018.11.002 2468-2179/© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) K.X Hau et al / Journal of Science: Advanced Materials and Devices (2018) 406e411 resistivity, no toxicity and low price [9e13] To tune the Curie temperature and improve the glass forming ability (GFA) for these materials, other elements such as Co, Ni, B, Y, Cr, Mn have been incorporated [9e17] However, the effects of the additional elements on the GFA and TC of the alloy were widely various For example, the Curie temperature of Fe90-xYxZr10 alloy increased from 225 K for x ¼ to 395 K for x ¼ 10 with increasing Y concentration [9] Both the saturation magnetization (Ms) and Curie temperature (TC) of the Fe-Zr-B alloy increased with a slight increase of B-concentration [12], while those of the Fe90-xMnxZr10 system decreased with increasing Mn concentration [14e16] These studies concentrated mainly on the La-Fe alloys with crystalline structure but hardly with amorphous structure In this work, we have investigated the influence of La addition on the structure, magnetic properties and magnetocaloric effect of Fe90-xLaxZr10 (x ¼ and 2) rapidly quenched ribbons prepared by the melt-spinning method A thorough analysis on the critical exponents and their association with the MCE near the paramagnetic-ferromagnetic (PM-FM) phase transition for these alloys has been made Experimental The alloys with nominal compositions of Fe90-xLaxZr10 (x ¼ and 2) were prepared from pure metals (99.9%) of Fe, La and Zr An arc-melting method was first used to ensure the homogeneity of the alloys The ribbons were then fabricated on a single wheel meltspinning system The quenching rate of the ribbons could be adjusted by changing the tangential velocity, v, of the copper wheel In this study, the ribbons were prepared with v ¼ 40 m/s All of the arc-melting and melt-spinning processes were performed under Ar atmosphere to avoid oxygenation The structure of the ribbons was analyzed by X-ray diffraction (XRD) The magnetic properties of the alloys were measured by a sample vibrating magnetometer (VSM) The magnetocaloric effect of the ribbons was assessed indirectly through determination of the magnetization versus magnetic field, M(H), at various temperatures, using Maxwell relationship Results and discussion The thickness of the obtained ribbons is about 15 mm Fig shows the XRD diffraction patterns of Fe90-xLaxZr10 alloy ribbons at room temperature The results reveal that the structural characteristic of the samples is quite similar All the ribbons have a coexistence of amorphous and crystalline phases The diffraction peaks corresponding to the crystalline phase of a-Fe and Fe2Zr are 407 observed in these patterns, although they are very weak This means that the prepared alloy ribbons are almost amorphous In our previous work [17], the undoped ribbons of Fe90Zr10 with different thicknesses were investigated Respectively, the undoped ribbons showed a large crystalline fraction and an amorphous structure with thicknesses of 30 mm and 15 mm The amorphous phase is mainly responsible for the magnetic properties and MCE of the Fe-Zr based alloy ribbons in the vicinity of room temperature Fig presents hysteresis loops at room temperature and reduced thermomagnetization curves (M/M100K) in a magnetic field of 100 Oe for Fe90-xLaxZr10 (x ¼ and 2) alloy ribbons From the hysteresis loops (Fig 2a), both the saturation magnetization Ms (approximately taken at H ¼ 12 kOe) and the coercivity Hc of the alloy ribbons were obtained The ribbons show a soft magnetic feature with low coercivity of less than 80 Oe (see the inset of Fig 2a) The Ms values determined for the samples with x ¼ and are ~30 and ~52 emu/g, respectively The Hc and Ms of the sample with x ¼ are 30 Oe and ~25 emu/g, respectively [17] Thus, the additional element of La slightly increases the Hc of the alloy Interestingly, the La addition significantly improves the Ms of the alloy The reduced thermomagnetization curves (Fig 2b) indicate that La clearly influences the TC of the alloy The value of TC was determined from the minimum of the dM/dT versus T curves (see insert of Fig 2b) The samples with x ¼ and have the TC values of 262 and 302 K, respectively The magnetization of both the samples does not reduce to zero after the magnetic phase transition This is probably due to the coexistence of the crystalline phases that have higher Curie temperatures, such as a-Fe This is in good agreement with the structural analysis (Fig 1) The TC value determined for the sample with x ¼ is 245 K [17] This means that the TC of the alloy increases with increasing La-concentration It should be noted that, the magnetic transition phase temperature of the alloy ribbons increased to room temperature with the La-concentration of at.% The effect of La-addition on the Curie temperature of the Fe-Zr based alloys has a significant meaning in controlling the working temperature of the magnetic refrigerants The enhancements of the Curie temperature and the saturation magnetization of the alloy by adding La can be explained by the strengthened coupling between 3d-electrons of Fe with 4f-ones of La The change in distance of FeFe atoms by the addition of La could also improve the ferromagnetic interaction in these alloys In order to investigate the MCE of the alloy ribbons, their magnetic entropy change DSm was calculated using the thermomagnetization data at various magnetic fields ranging from 0.01 to 12 kOe (Fig 3) From these thermomagnetization curves, we deduced the magnetization versus magnetic field, M(H), at various temperatures (Fig 4) According to our previous results [17,18], we compared the data deduced from the thermomagnetization curves with those from the virgin magnetization ones and we found a good agreement between these two methods Then, the magnetic entropy change, DSm, is determined from the M(H) data by using the following relation: ðH DSm ¼ À  vM dH vT (1) Fig XRD patterns of Fe90-xLaxZr10 ribbons The temperature dependence of -DSm of the Fe90-xLaxZr10 ribbons for different magnetic field changes (DH ¼ 4, 6, 8, 10 and 12 kOe) is represented in Fig It can be observed that the value of DSm increases with increasing the magnetic field change For DH ¼ 12 kOe, the maximum magnetic entropy change, jDSmjmax, determined for the samples with x ¼ and are 1.0 and 1.1 J∙kgÀ1KÀ1, respectively These values are equivalent or higher than those reported in the literature for rapidly quenched Fe-based 408 K.X Hau et al / Journal of Science: Advanced Materials and Devices (2018) 406e411 Fig Hysteresis loops at room temperature (a) and reduced thermomagnetization curves in an applied magnetic field of 100 Oe (b) of Fe90-x LaxZr10 (x ¼ and 2) ribbons The insets of Fig 2a and Fig 2b respectively show the ways to determine the coercivity and the Curie temperatures of the ribbons Fig Thermomagnetization curves in different magnetic fields for Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) Fig Magnetization vs magnetic field at various temperatures deduced from the thermomagnetization curves (Fig 3) for Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) MCE alloys, including Fe-Mn-Zr [15], Fe-Cr-Mo-Cu-Ga-P-C-B [19], Fe-Mo-Cu-B [20], (Fe85Co5Cr10)91Zr7B2 [21], (Fe70Ni30)89Zr7B4 [22,23], Fe-Zr-Cr [24], Fe-Y-Zr [25], Fe-Zr-B-Cu [26], and Fe-Nb-B [27] The refrigerant capacity (RC) of the samples, which is defined as the product of the maximum entropy change (jDSmjmax) and the full width at half maximum (dTFWHM) of the entropy change peak, was also calculated The value of dTFWHM was also referred as the working temperature range of a magnetic refrigerant The working temperature range of these ribbons is determined to be about 45 and 67 K for x ¼ and 2, respectively The maximum RC of about 74 J∙kgÀ1 around room temperature was achieved for the at.% Laadded sample To clearly understand the critical magnetic behavior near the second order PM-FM phase transition for the present ribbons, the Arrott plots or M2-H/M plots were constructed from the M(H) data and the results are shown in Fig Because the PM-FM transition at the Curie temperature is a continuous phase transition, the power K.X Hau et al / Journal of Science: Advanced Materials and Devices (2018) 406e411 409 Fig DSm(T) curves (DH ¼ 4, 6, 8, 10 and 12 kOe) for Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) Fig M2-H/M plots at different temperatures for Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) law dependence of spontaneous magnetization Ms(T) and inverse initial susceptibility c-10(T) on reduced temperature ε with the set of critical exponents of b, g, d etc., can be determined by using the following ArrotteNoakes relations [28]: MS Tị ẳ M0 ịb c1 Tị ẳ H0 g M0 H ẳ DM1=d ε0 (3) ε¼0 (4) where M0, H0 and D are the critical amplitudes and ε ¼ ðΤ À ΤC Þ=TC is the reduced temperature The d parameter can be calculated using the Widom scaling relation [29]: d ¼ ỵ g=b (5) The spontaneous magnetization Ms(T) and inverse initial susceptibility c-10(T) of the ribbons can be obtained from constructing and linearly fitting of Arrott plot of M2 versus H/M at high magnetic fields The values of Ms(T) and c-10(T) as functions of temperature T are plotted for the Fe90-xLaxZr10 ribbons (Fig 7) In accordance with equations (2) and (3) for Ms(T) and c-10(T), the power law fittings are used to extract b, g and TC (Fig 7) The resulted values of b and g were then used to calculate the d parameter based on equation (5) As a result, the sample with x ¼ has the critical parameters of b z 0.437, g z 0.834, d z 2.91 and TC z 262 K Similarly, for the sample with x ¼ 2, those values are b z 0.445, g z 1.178, d z 3.64 and TC z 301 K The values of TC of the alloys obtained from the fittings are mostly equal to those directly determined from the thermomagnetization measurements This means that the procedures for calculating the critical exponents are correct By using the Kouvel - Fisher method [30], the critical parameters of the alloy ribbons can be obtained more accurately Similar to the ArrotteNoakes method, the values of MS(T) and cÀ1 (T) are also determined by plotting M1/b versus (H/M)1/g curves Then, the critical parameters TC, b and g can be obtained from fitting MS(T) and cÀ1 (T) data by using the following relations: Ms TịẵdMs =dT1 ẳ T Tc ị=b h c1 Tị dc0 Tị=dT i1 ẳ T Tc Þ=g (6) (7) Fig indicates the KouveleFisher curves for the alloy ribbons As shown in this figure, the fitting results of the critical parameters yield b z 0.432, g z 0.843 and TC z 263 K for the x ¼ sample and b z 0.448, g z 1.180 and TC z 302 K for the x ¼ sample By using the relation (5), the d values of the samples are calculated to be 2.951 for x ¼ and 3.634 for x ¼ The values of the critical parameters obtained from the KouveleFisher method are in good agreement with those determined from the ArrotteNoakes fittings In comparison with some standard models, such as the meanfield theory (b ¼ 0.5, g ¼ and d ¼ 3.0), 3D-Heisenberg model (b ¼ 0.365, g ¼ 1.336 and d ¼ 4.8) and 3D-Ising model (b ¼ 0.325, g ¼ 1.241 and d ¼ 4.82 [31], the critical parameters attained for the 410 K.X Hau et al / Journal of Science: Advanced Materials and Devices (2018) 406e411 Fig Temperature dependence of spontaneous magnetization Ms(T) and inverse initial susceptibility cÀ1 (T) of the Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) Fig KouveleFisher plots for Fe90-xLaxZr10 ribbons with x ¼ (a) and x ¼ (b) Fe90-xLaxZr10 alloy ribbons are close to those of the mean field theory of long-range ferromagnetic order This means that the samples are mainly of long-range ferromagnetic order The fact that the critical parameters of the samples fall between those of the mean-field and 3D-Heisenberg models reveals part of short-range magnetic orders coexisting with the long-range magnetic orders in the alloy ribbons According to the previous study [32], the asquenched Fe90Zr10 ribbons show a short-range ferromagnetic order with b ¼ 0.365 and g ¼ 1.615 This may suggests that the critical parameters of the Fe-Zr based alloys with La-addition are closer those of the mean field theory of long-range ferromagnetic orders The addition of La plays an important role in establishing the longrange ferromagnetic order in the Fe90-xLaxZr10 ribbons The dominance of the long-range ferromagnetic order is consistent with the enhancements of the Curie temperature and saturation magnetization observed for the La-added alloy ribbons It is the coexistence of long- and short-range ferromagnetic orders that broadens the working temperature range of the Fe-La based alloys Conclusion The influence of La addition on the structure, magnetic properties, magnetocaloric effect and critical parameters of Fe90xLaxZr10 (x ¼ and 2) ribbons was investigated systematically The Curie temperature of these alloys can be tuned to the region of room temperature by choosing an appropriate La-concentration The maximum entropy change, jDSmjmax ¼ 1.1 J∙kgÀ1KÀ1 for DH ¼ 12 kOe and the wide working range around room temperature, DT ~70 K, reveal potential use of the rapidly-quenched Fe-LaZr based alloys in magnetic refrigerators A detailed analysis of the critical parameters of the Fe90-xLaxZr10 ribbons indicates the dominance of long-range ferromagnetic order that coexists with a short-range magnetic order Controlling the ratio of these phases may provide an effective way for tuning the magnetocaloric effect and broadening the working temperature range of magnetocaloric materials Acknowledgments This work was supported by Vietnam Academy of Science and Technology under grants No VAST.HTQT.NGA.05/17-18 and No HTCBT14.18, and by Russian Foundation for Basic Research under grant No 17-58-540002 A part of the work was done in Key Laboratory for Electronic Materials and Devices and Laboratory of Magnetism and Superconductivity, Institute of Materials Science, Viet Nam The work at Chungbuk National University supported by the National Research Foundation of Korea through the Korea Russia Joint Collaboration (No 2017K1A3A1A49070064) References [1] V.K Pecharsky, K.A Gschneidner 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Ms(T) and inverse initial susceptibility c-10(T) of the ribbons can be obtained from constructing and linearly fitting of Arrott plot of M2 versus H/M at high magnetic fields The values of Ms(T) and. .. Thanh, M.H Phan, S.C Yu, Coexistence of conventional and inverse magnetocaloric effects and critical behaviors in Ni50Mn50-xSnx (x ¼ 13 and 14) alloy ribbons, Appl Phys Lett (Nov 2012) 212403 K.X