Giant low-field magnetocaloric effect in single-crystalline EuTi0.85Nb0.15O3

Abstract

The magnetocaloric effect in ferromagnetic single crystal EuTi0.85Nb0.15O3 has been investigated using magnetization and heat capacity measurements. EuTi0.85Nb0.15O3 undergoes a continuous ferromagnetic phase transition at TC = 9.5 K due to the long range ordering of magnetic moments of Eu2+ (4f7). With the application of magnetic field, the spin entropy is strongly suppressed and a giant magnetic entropy change is observed near TC. The values of entropy change ΔSm and adiabatic temperature change ΔTad are as high as 51.3 J kg−1 K−1 and 22 K, respectively, for a field change of 0–9 T. The corresponding magnetic heating/cooling capacity is 700 J kg−1. This compound also shows large magnetocaloric effect even at low magnetic fields. In particular, the values of ΔSm reach 14.7 and 23.8 J kg−1 K−1 for field changes of 0–1 T and 0–2 T, respectively. The low-field giant magnetocaloric effect, together with the absence of thermal and field hysteresis makes EuTi0.85Nb0.15O3 a very promising candidate for low temperature magnetic refrigeration.

Giant magnetocaloric effect in an exchange-frustrated GdCrTiO5 antiferromagnet

“…In this context, it may be noted that undoped and doped EuTiO 3 , EuDy 2 O 4 and GdVO 4 exhibit huge MCE at low temperature. 49,50,[52][53][54] The values of ∆S max m in these compounds are also comparable to the present system. However, for the above mention compounds, ∆S m (T ) shows a strong decrease in the low-temperature region.…”

High spin-polarization in the low Curie temperature complex itinerant ferromagnet EuTi$_{1-x}$Nb$_x$O$_3$

“…Substitution by Nb 4+ ion at the Ti 4+ results in the introduction of electrons in EuTiO 3 without disturbing the Eu 2+ moments chain. Previous studies in EuTi 1x Nb x O 3 revealed notable increase in electrical conductivity and large values of magnetocaloric response of about 23.8 J kg −1 K −1 even at low magnetic field 0-2 T [11]. Therefore, introduction of Nb in antiferromagnetic EuTiO 3 results in ferromagnetic behaviour in EuTi 1−x Nb x O 3 (x = 0.15) with T C ∼ 9.5 K and saturation magnetization at 2 K is estimated to be ∼ 7µ B /Eu [11].…”

“…There has been a considerable amount of theoretical and experimental * goutam@iisermohali.ac.in work done for understanding the nature of the ground state in this family. Among the perovskites, EuTiO 3 with unique divalent rare-earth ion Eu and tetravalent Ti has generated substantial interest since the discovery of magnetoelectric coupling in this compound below the antiferromagnetic (AFM) transition temperature T N = 5.5 K [8][9][10][11][12][13]. EuTiO 3 has a positive Curie-Weiss constant and exhibits strong coupling between magnetic ordering and phonon modes.…”

Viable Materials with a Giant Magnetocaloric Effect

“…A few contain precious Rh (e.g., FeRh [24,222,278,279] and Tb 3 Rh [270]). Many contain critical rare earth, such as Eu in Eu 2 In [140], EuTiO 3 [114,135,156,195] doped with Al [113], Cr [196], Mn [134], Co [151], Ni [119], Ba [157,206], Nb [110,170,195] and Eu in other compounds [133,232,240,251]; Gd in GdAlO 3 [158], GdFeO 3 [138,162], GdCrO 3 [183], GdCrO 4 -ErCrO 4 [202], GdScO 3 [117,124], Gd 2 CoMnO 6 [155], Gd 2 BaNiO 5 [152], GdCrTiO 5 [143], GdCo 2 B 2 [271], GdCoC 2 [171], RuSr 2 GdCu 2 O 8 [208], etc. ; Tb in TbFeO 3 [176], TbMn 2 O 5 [179], Tb 2 CoMnO 6 [132], Tb 5 Ge 2−x Si 2−x Mn 2x [255], Tb 4 Gd 1 Si 2.035 Ge 1.935 Mn 0.03 [197], etc.…”