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EuTiO3是直接带隙半导体材料，在液氦温度附近呈现反铁磁性，且具有较大的磁熵变，但是当其转变为铁磁性时，可以有效提高低磁场下的磁熵变.本文通过元素替代，研究晶格常数的变化和电子掺杂对磁性和磁热效应的影响.实验采用溶胶凝胶法制备EuTiO3和Eu0.9M0.1TiO3（M=Ca，Sr，Ba，La，Ce，Sm）系列样品.结果表明：大离子半径的碱土金属离子替代提高了铁磁性耦合，有利于提高低磁场下的磁热效应.电子掺杂可以抑制其反铁磁性耦合从而使其表现为铁磁性.当大离子半径的稀土La和Ce离子替代Eu离子时，既增大了晶格常数也实现了电子掺杂，表现出较强的铁磁性.在1 T的磁场变化下，Eu0.9La0.1TiO3和Eu0.9Ce0.1TiO3的最大磁熵变分别为10.8和11 J/（kg· K），均大于EuTiO3的9.8 J/（kg· K）；制冷能力分别为39.3和51.8 J/kg，相对于EuTiO3也有所提高.EuTiO3 is a direct band-gap semiconductor material and exhibits antiferromagnetism with large magnetic entropy change around the liquid helium temperature. The ferromagnetic state can be changed into antiferromagnetic state through lattice constant change and electron doping by element substitution due to strong spin-lattice coupling coexistence of ferromagnetic coupling, and antiferromagnetic coupling. The values of magnetic entropy change can be effectively improved under low magnetic field change after changing into ferromagnetism. Samples of EuTiO3 and Eu0.9M0.1TiO3 (M=Ca, Sr, Ba, La, Ce, Sm) are prepared by the sol gel method. The Eu0.9Ca0.1TiO3 exhibits the antiferromagnetism due to similar ion radius. The ferromagnetic coupling between Eu0.9Sr0.1TiO3 and Eu0.9Ba0.1TiO3 is enhanced, for alkaline earth metal (Sr and Ba) has larger ion radius, which is beneficial to improving the magnetocaloric effect under low magnetic field. Electron doping can inhibit the antiferromagnetic coupling because the extra carrier may occupy the Ti 3d and reduce the hybridization of Eu 4f-Ti 3d-Eu 4f. When the electron doping concentration is greater than 10%, the spin polarization rate of Ti 3d state on the Fermi surface is negative, resulting in the transition from antiferromagnetic to ferromagnetic state. When the Eu ions are replaced with the Sm ions (Sm ion radius is similar to Eu ion radius), the ferromagnetic coupling is enhanced. However, when the Eu ions are replaced with the La or Ce ions, the samples show strong ferromagnetism, for the lattice constant and electron doping are increased. A giant reversible magnetocaloric effect and large refrigerant capacity for each of Eu0.9M0.1TiO3 (M=Sr, Ba, La, Ce) compounds are observed. Under the magnetic field change of 1 T, the values of maximum magnetic entropy change and refrigeration capacity are 9.8 J/(kg·K) and 36.6 J/kg for Eu0.9Sr0.1TiO3, and 10 J/(kg·K) and 45.1 J/kg for Eu0.9Ba0.1TiO3. The values of maximum magnetic entropy change of Eu0.9La0.1TiO3 and Eu0.9Ce0.1TiO3 are 10.8 J/(kg·K) and 11 J/(kg·K), respectively, which are larger than that of EuTiO3 (9.8 J/(kg·K)). The values of refrigeration capacity are 39.3 J/kg and 51.8 J/kg, which are also improved compared with those of EuTiO3. In a word, the results suggest that these compounds could be considered as good candidates for low-temperature and low-field magnetic refrigerant.
[1] Benford S M, Brown G V 1981 J. Appl. Phys. 52 2110
[2] Shen B G, Sun J R, Hu F X, Zhang H W, Chen Z H 2009 Materials. Adv. Mater. 21 4545
[3] Tegus O, Bruck E, Buschow K H, DeBoer F R 2002 Nature 415 150
[4] Zhang H, Shen B G, Xu Z Y, Shen J, Hu F X, Sun J R, Long Y 2013 Appl. Phys. Lett. 102 092401
[5] Gupta S B, Suresh K G 2013 Appl. Phys. Lett. 102 022408
[6] Mo Z J, Shen J, Yan LQ, Wu J F, Wang L C, Tang C C, Shen B G 2013 Appl. Phys. Lett. 102 192407
[7] Chen J, Shen B G, Dong Q Y, Sun J R 2010 Solid State Commun. 150 1429
[8] Li L W, Saensunon B, Hutchison W D, Huo D X, Nishimura K 2014 J. Alloys Compd. 582 670
[9] Cui L, Wang L C, Dong Q Y, Liu F H, Mo Z J, Zhang Y, Niu E, Xu Z Y, Hu F X, Sun J R, Shen B G 2015 J. Alloys Compd. 622 24
[10] Li L, Hutchison W D, Huo D X, Namiki T, Qian Z H, Nishimura K 2012 Scr. Mater. 67 237
[11] Li L W, Namiki T, Huo D X, Qian Z H, Nishimura K 2013 Appl. Phys. Lett. 103 222405
[12] Mo Z J, Shen J, Yan L Q, Tang C C, Lin J, Wu J F, Sun J R, Wang L C, Zheng X Q, Shen B G 2013 Appl. Phys. Lett. 103 052409
[13] Balli M, Jandl S, Fournier P, Gospodinov M M 2014 Appl. Phys. Lett. 104 232402
[14] Balli M, Jandl S, Fournier P, Mansouri S, Mukhin A, Ivanov Yu V, Balbashov A M 2015 J. Magn. Magn. Mater. 374 252
[15] Alho B P, Magnus A, Carvalho G, von Ranke P J 2014 J. Appl. Phys. 116 113907
[16] Scagnoli V, Allieta M, Walker H, Scavini M, Katsufuji T, Sagarna L, Zaharko O, Mazzoli C 2012 Phys. Rve. B 86 094432
[17] Guguchia Z, Keller H, Kremer R K, J Köhler, Luetkens H, Goko T, Amato A, Bussmann-Holder A 2014 Phys. Rve. B 90 064413
[18] Akamatsu H, Kumagai Y, Oba F, Fujita K, Murakami H, Tanaka K, Tanaka L 2011 Phys. Rev. B 83 214421
[19] Mo Z J, Hao Z H, Deng J Z, Shen J, Li L, Wu J F, Hu F X, Sun J R, Shen B G 2017 J. Alloys Compd. 694 235
[20] Mo Z J, Sun Q L, Wang C H, Wu H Z, Li L, Meng F B, Tang C C, Zhao Y, Shen J 2017 Ceram. Int. 43 2083
[21] Li W W, Zhao R, Wang L, Tang R J, Zhu Y Y, Lee J H, Cao H X, Cai T Y, Guo H Z, Wang C, Ling L S, Pi L, Jin K J, Zhang Y H, Wang H Y, Wang Y Q, Ju S, Yang H 2013 Sci. Rep. 3 2618
[22] Rubi K, Midya A, Mahendiran R, Repaka D V M, Ramanujan R V 2016 J. Appl. Phys. 119 243901
[23] Mo Z J, Sun Q L, Shen J, Mo Y, Li Y J, Li L, Liu G D, Tang C C, Meng F B 2018 Chin. Phys. B 27 017501
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[1] Benford S M, Brown G V 1981 J. Appl. Phys. 52 2110
[2] Shen B G, Sun J R, Hu F X, Zhang H W, Chen Z H 2009 Materials. Adv. Mater. 21 4545
[3] Tegus O, Bruck E, Buschow K H, DeBoer F R 2002 Nature 415 150
[4] Zhang H, Shen B G, Xu Z Y, Shen J, Hu F X, Sun J R, Long Y 2013 Appl. Phys. Lett. 102 092401
[5] Gupta S B, Suresh K G 2013 Appl. Phys. Lett. 102 022408
[6] Mo Z J, Shen J, Yan LQ, Wu J F, Wang L C, Tang C C, Shen B G 2013 Appl. Phys. Lett. 102 192407
[7] Chen J, Shen B G, Dong Q Y, Sun J R 2010 Solid State Commun. 150 1429
[8] Li L W, Saensunon B, Hutchison W D, Huo D X, Nishimura K 2014 J. Alloys Compd. 582 670
[9] Cui L, Wang L C, Dong Q Y, Liu F H, Mo Z J, Zhang Y, Niu E, Xu Z Y, Hu F X, Sun J R, Shen B G 2015 J. Alloys Compd. 622 24
[10] Li L, Hutchison W D, Huo D X, Namiki T, Qian Z H, Nishimura K 2012 Scr. Mater. 67 237
[11] Li L W, Namiki T, Huo D X, Qian Z H, Nishimura K 2013 Appl. Phys. Lett. 103 222405
[12] Mo Z J, Shen J, Yan L Q, Tang C C, Lin J, Wu J F, Sun J R, Wang L C, Zheng X Q, Shen B G 2013 Appl. Phys. Lett. 103 052409
[13] Balli M, Jandl S, Fournier P, Gospodinov M M 2014 Appl. Phys. Lett. 104 232402
[14] Balli M, Jandl S, Fournier P, Mansouri S, Mukhin A, Ivanov Yu V, Balbashov A M 2015 J. Magn. Magn. Mater. 374 252
[15] Alho B P, Magnus A, Carvalho G, von Ranke P J 2014 J. Appl. Phys. 116 113907
[16] Scagnoli V, Allieta M, Walker H, Scavini M, Katsufuji T, Sagarna L, Zaharko O, Mazzoli C 2012 Phys. Rve. B 86 094432
[17] Guguchia Z, Keller H, Kremer R K, J Köhler, Luetkens H, Goko T, Amato A, Bussmann-Holder A 2014 Phys. Rve. B 90 064413
[18] Akamatsu H, Kumagai Y, Oba F, Fujita K, Murakami H, Tanaka K, Tanaka L 2011 Phys. Rev. B 83 214421
[19] Mo Z J, Hao Z H, Deng J Z, Shen J, Li L, Wu J F, Hu F X, Sun J R, Shen B G 2017 J. Alloys Compd. 694 235
[20] Mo Z J, Sun Q L, Wang C H, Wu H Z, Li L, Meng F B, Tang C C, Zhao Y, Shen J 2017 Ceram. Int. 43 2083
[21] Li W W, Zhao R, Wang L, Tang R J, Zhu Y Y, Lee J H, Cao H X, Cai T Y, Guo H Z, Wang C, Ling L S, Pi L, Jin K J, Zhang Y H, Wang H Y, Wang Y Q, Ju S, Yang H 2013 Sci. Rep. 3 2618
[22] Rubi K, Midya A, Mahendiran R, Repaka D V M, Ramanujan R V 2016 J. Appl. Phys. 119 243901
[23] Mo Z J, Sun Q L, Shen J, Mo Y, Li Y J, Li L, Liu G D, Tang C C, Meng F B 2018 Chin. Phys. B 27 017501
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