The Magnetocaloric Effect Of EuTiO₃ At Low Temperature

Magnetic refrigeration technology was a kind of environmental protection technology which could effectively expand the refrigeration application in the low temperature region of liquid helium.Titanium oxide magnetic refrigeration materials with perovskite structure have attracted much research attention because of their large magnetic entropy change,better chemical stability,adjustable Curie temperature,lower production cost and use cost,non-toxic and other advantages under low magnetic field.In this paper,the crystal structure and magnetothermal effect of EuTiO₃after B-site ion substitution were characterized,and its working mechanism was analyzed.The contents are as follows:Fe²⁺,Ni²⁺ and Co²⁺ were introduced to replace the metal cations Ti⁴⁺ in EuTiO₃,and the magnetic structure of EuTiO₃ was changed by hole doping.The magnetic transformation and magnetothermal effect mechanism of the substituted EuTiO₃ were analyzed.In addition to the lattice distortion of EuTiO₃,the substitution of Fe²⁺,Ni²⁺ and Co²⁺ ions for Ti⁴⁺ at B site would form holes and occupy the Eu4f,which would destroy the AFM superexchange between Eu 4f-Ti 3d-Eu 4f.The results showed that the widest temperature range is observed in Eu Ti_0.875Fe_0.125O₃sample at low magnetic field,and the maximum value was 11.1 J/kg K at a magnetic field strength of 10 k Oe.The best magnetic refrigeration capacity is reached to 325 J/kg in high magnetic field for Eu Ti_0.875Coe_0.125O₃.By substituting the metal cations Ti⁴⁺ in EuTiO₃ with high valence P⁵⁺?Nb⁵⁺ and V⁵⁺,an extra electron was introduced to occupy the t_2g space orbit ofTi3d,which restrained the AFM super exchange between Eu4f-Ti3d-Eu4f,destroyed the balance between AFM and FM by FM dominanting.In discussing the-?S_Mand RC value,Eu Ti_0.85Nb_0.15O₃ sample has the best magnetocaloric effect and the highest RC value.The-?S_M^max value could reach 13.1 J/kg K and RC value was 86 J/kg at a magnetic field strength of 10 k Oe.The influence of Mn-Ni B-site both substitution on the magnetothermal effect of EuTiO₃ was carried out.The AFM coupling of EuTiO₃ compound under low magnetic field was inhibited,the FM coupling was enhanced.At low temperature,it shows FM state and its saturation susceptibility increases.A series of Eu Ti_0.9135(Mn_0.0625Ni_0.025)O₃(x=0.025,0.05,0.075,0.1) samples were obtained.Compared with the samples replaced by Mn alone,the samples with x=0.025concentration has higher-?S_Mmaxvalue and wider half height width than the samples with single Mn introductiong.The RC value was 62 J/kg at a magnetic field strength of 10 kOe.