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Magnetostructural phase transition in Ga-doped MnNiGe compounds



The magnetic phase transitions in MnNiGe1 − xGax (x = 0.0725, 0.080, and 0.085) compounds were investigated by dc magnetization measurements. Due to the introduction of Ga, all the compounds crystallized in Ni2In-type structure at room temperature instead of TiNiSi-type structure for their parent compound MnNiGe. With increasing temperature, each compound goes through two magnetic phase transitions, i.e. magnetostructural phase transitions from antiferromagnetic (AFM) TiNiSi-type phase to ferromagnetic (FM) Ni2In-type phase and ferromagnetic to paramagnetic (FM–PM) transition of Ni2In-type phase. It was found that the magnetostructural phase transition temperatures Tt decreased with the increase of Ga content, while the FM–PM transition temperature TC almost did not change. Large inverse magnetic entropy ΔSM in the vicinity of Tt following a conventional one around TC was observed for each sample.