Critical behavior and magnetocaloric effect in Mn-doped Eu8Ga14Mn2Ge30type-I clathrate

Abstract

Exploration of magnetic 3d element doped clathrate Eu8Ga16Ge30 is an important field in clathrate studies. It covers complicated magnetic interactions among the moments of 3d- and 4f-atoms. In the current study, the Mn-doped sample with nominal composition of Eu8Ga14Mn2Ge30 was prepared by the melt spinning technique. The incorporation of Mn into the lattice leads to a decrease in lattice parameters. Magnetization and modified Arrott plots indicate that the Mn-doped sample undergoes a second-order ferromagnetic-paramagnetic phase transition at ∼29.9 K, which is about 5 K lower than that of Mn-free Eu8Ga16Ge30 (TC ∼ 34.7 K). The critical behavior around TC is investigated and critical values of β = 0.35, γ = 0.85, and δ = 3.43 are calculated. In addition, a huge magnetic entropy change (-ΔSM) improvement is observed due to Mn-doping. The sample shows a large −ΔSMmax of ∼6.80 J/kg K around TC for a field change of 3 T. This is 17% higher than that of Mn-free Eu8Ga16Ge30. It is speculated that the substitution of Mn for Ga can introduce new 4f-3d exchange interactions that can lead to a more rapid magnetization process. The excellent magnetocaloric effect suggests the Mn-doped Eu8Ga16Ge30 could be expected to have effective applications for low temperature magnetic refrigeration.