Observation of Griffiths phase, spin glass behaviour and magnetocaloric effect in frustrated Ga2Mn2-xCrxO7 (x = 0, 0.1, 0.3, 0.5) pyrochlore compounds

Abstract

New series of pyrochlore compounds Ga2Mn2-xCrxO7 (x = 0–0.5) has been synthesized by conventional solid-state reaction method. The X-ray diffraction analysis confirms a single-phase cubic structure of the prepared compounds. All compounds undergo a paramagnetic-antiferromagnetic transition at the Néel transition temperature, close to 42 K. Below ∼12 K temperature, magnetization measurements reveal a glassy behaviour. The value of frustration parameter indicates the presence of a spin frustration. All the compounds exhibit the Griffiths phase. The Arrott's plots confirmed a second-order magnetic phase transition. Moreover, under 5 T applied magnetic field, the maximum value of magnetic entropy change −ΔS was 1.36 J/kg.K for Ga2Mn2O7 compound, which slightly increased to 1.47 J/kg.K for the compound with x = 0.5. At 21 K, the relative cooling power value enhanced from 42.96 J/kg to 47.73 J/kg with Cr4+-ion content changing from x = 0 to x = 0.5.