DSpace at VNU: Large magnetic-entropy change above room temperature in the colossal magnetoresistance La0.7Sr0.3Mn1-xNixO3 materials

ARTICLE IN PRESS Journal of Magnetism and Magnetic Materials 272–276 (2004) 1295–1297 Large magnetic-entropy change above room temperature in the colossal magnetoresistance La0.7Sr0.3Mn1ÀxNixO3 materials Md.A Choudhurya, S Akhtera, D.L Minhb, N.D Thoc, N Chauc,* b a Atomic Energy Center, 4, Kazi Nazrul Islam Avenue, P.O Box-164, Ramna, Dhaka 1000, Bangladesh Department of Solid State Physics, Vietnam National University, Hanoi, 334 Nguyen Trai, Ha Noi, Viet Nam c Center for Materials Science, Vietnam National University, Hanoi 844, 334 Nguyen Trai, Hanoi, Viet Nam Abstract Magnetic and magnetocaloric properties of the series La0.7Sr0.3Mn1ÀxNixO3 (x ¼ 0:00; 0.01, 0.02, 0.03, and 0.05) have been investigated The X-ray diffraction analysis shows that all perovskites studied have the rhombohedral structure The field-cooled and zero-field-cooled thermomagnetic curves measured at low field show that there is spinglass (or cluster-glass)-like state in the samples It is found that the magnetic-entropy change jDSmax j has reached the highest value of 3.54 J/kg K at 13.5 kOe for the composition with x ¼ 0:02: r 2004 Elsevier B.V All rights reserved PACS: 75.30.Sg Keywords: Magnetic refrigeration; Manganites; Magnetic measurements; Perovskite manganites; Phase transitions A magnetic-field-induced magnetic-entropy change is a well-known basis of technique for magnetic refrigeration The largest reported value of jDSM j in the group of rare earths and their alloys [1], it is 13.7 J/kg K for pure Gd, which undergoes a ferromagnetic-phase transition Gd is thought to be the optimum magnetic refrigerant close to near room temperature It is of interest to seek other systems which exhibit magnetic-phase transition in the neighbourhood of room temperature One such system is perovskite-like manganese oxides RE1ÀxAxMnO3 (where RE is a trivalent rareearth ion and A is a divalent ion such as Ca, Sr, Ba, or Pb) due to their colossal magnetoresistance In this paper, we measured the magnetic-entropy change of Ni-substituted La0.7Sr0.3Mn1ÀxNixO3 perovskite The manganites La0.7Sr0.3Mn1ÀxNixO3 (x ¼ 0:00; 0.01, 0.02, 0.03, and 0.05) are prepared by the conventional solid-state reaction technique (the nominal values of x are 0.00, 0.01, 0.02, 0.03, and 0.05) *Corresponding author Tel.: +84-4-5582216; fax: +84-48589496 E-mail address: chau@cms.edu.vn (N Chau) Fig shows the SEM photograph of sample La0.7Sr0.3Mn0.97Ni0.03O3 with homogeneous microstructure The X-ray diffraction analysis shows that the perovskites are of single phase with rhombohedral structure We can see from Table that the lattice parameters of the samples are slightly changing with x: Fig shows the thermomagnetic field-cooled (FC) and zero-field-cooled (ZFC) curves of sample La0.7Sr0.3Mn0.98Ni0.02O3 measured in magnetic field of 20 Oe Below Curie temperature magnetization of the samples decreases with decreasing temperature, i.e in this region the predominant antiferromagnetic phase coexists and competes with the ferromagnetic phase at low temperature The role of grain boundaries and grain surface could be a reason of such phenomenon At grain boundary, exchange interactions (super exchange and double exchange) are weak compared to those inside the grain This leads to the inhomogeneity of magnitude of exchange interaction In addition, crystal structure at grain boundary is often distorted, only short-range order remains and structure is similar to spin glass, leading to frustration feature to occur easily [2] Thus, spin-glass (or cluster-glass) state indicated by large 0304-8853/$ - see front matter r 2004 Elsevier B.V All rights reserved doi:10.1016/j.jmmm.2003.12.078 ARTICLE IN PRESS Md.A Choudhury et al / Journal of Magnetism and Magnetic Materials 272–276 (2004) 1295–1297 1296 Fig SEM picture of surface with x ¼ 0:03: Table Lattice parameters of the La0.7Sr0.3Mn1ÀxNixO3 samples Sample ( a (A) ( b (A) ( c (A) c=a ( 3) V (A x ¼ 0:00 x ¼ 0:01 x ¼ 0:02 x ¼ 0:03 x ¼ 0:05 5.486 5.491 5.489 5.490 5.489 5.486 5.491 5.489 5.490 5.489 13.327 13.343 13.359 13.324 13.312 2.429 2.430 2.434 2.426 2.425 347.04 348.24 348.48 347.96 347.40 Fig (a) Isothermal magnetization curves around TC and (b) magnetic-entropy change as a function of temperature for sample La0.7Sr0.3Mn0.98Ni0.02O3 Fig Thermomagnetic FC and ZFC curves for sample with x ¼ 0:02: irreversible change of magnetization below TC can be understood by freezing of cluster glass The small amount of substitution leads to weakening of double exchange; hence, TC slightly decreases from 350 to 320 K when x increases from 0.00 to 0.05 Fig shows the isothermal magnetization curves for sample with x ¼ 0:02 measured at 13.5 kOe (Fig 3a) and magnetic-entropy change jDSj as a function of tempera- ture (Fig 3b) One can see that jDSmax j has reached the rather high value of 3.54 J/kg K with x ¼ 0:02: The rest of the values for the other samples are 2.67 J/kg K (x ¼ 0:01), 3.15 J/kg K (x ¼ 0:03), and 2.33 J/kg K (x ¼ 0:05) Note that the Ni concentrations are balanced with errors of less than 0.1% In conclusion, the five compositions La0.7Sr0.3Mn1ÀxNixO3 (x ¼ 0:00; 0.01, 0.02, 0.03, and 0.05) were prepared with single phase and exhibited rhombohedral structure There is spin-glass (or cluster-glass)-like state in the samples The Curie temperature slightly decreases with increasing amount of Ni substitution The maximum value of magnetic-entropy change jDSmax j has reached the highest value of 3.54 J/kg K at 13.5 kOe for the composition with x ¼ 0:02: Our investigated samples could be considered as suitable candidate for working substance in magnetic refrigeration technology at temperature region above room temperature We would like to thank project 420101 of Vietnam National Program for Fundamental Research and IPPS of Uppsala University-Sweden for support of this work ARTICLE IN PRESS Md.A Choudhury et al / Journal of Magnetism and Magnetic Materials 272–276 (2004) 1295–1297 References [1] V.K Pecharsky, K.A Gschneidner, J Magn Magn Mater 167 (1997) 1179 1297 [2] Zhi Hong Wang, Tian Hao Ji, Yi Qian Wang, Xin Chen, Run Wie Li, Jian Wang Cai, Ji Rong Sun, Bao Geu Shen, Chun Hua Yan, J Appl Phys 87 (2000) 5582  ... structure There is spin-glass (or cluster-glass)-like state in the samples The Curie temperature slightly decreases with increasing amount of Ni substitution The maximum value of magnetic-entropy change. .. reached the highest value of 3.54 J/kg K at 13.5 kOe for the composition with x ¼ 0:02: Our investigated samples could be considered as suitable candidate for working substance in magnetic refrigeration... function of tempera- ture (Fig 3b) One can see that jDSmax j has reached the rather high value of 3.54 J/kg K with x ¼ 0:02: The rest of the values for the other samples are 2.67 J/kg K (x ¼ 0:01), 3.15