Materials Research Express (Jan 2024)
Effect of x-ray irradiation on magnetocaloric materials, (MnNiSi)1-x(Fe2Ge)x and LaFe13-x-yMnxSiyHz
Abstract
Understanding the behavior of magnetocaloric materials when exposed to high-energy x-ray irradiation is pivotal for advancing magnetic cooling technologies under extreme environments. This study investigates the magnetic and structural changes of two well-studied magnetocaloric materials, (MnNiSi) _1−x (Fe _2 Ge) _x composition (x = 0.34) and LaFe _13-x-y Mn _x Si _y H _z composition (x = 0.30,y = 0.1.26 and z = 1.53) alloys upon irradiation. The alloys were exposed to x-ray radiation with a dosage of a continuous sweeping rate of ∼>120 Gy min ^−1 and an absorbed dose of 35 kGy . Both the samples didn’t show any observable crystal change after irradiation. There was a considerable change in magnetization at low applied magnetic fields in magnetization versus temperature measurements from 2.72 emu g ^−1 to 4.01 emu g ^−1 in the irradiated (MnNiSi) _1−x (Fe _2 Ge) _x sample and 4.41 emu g ^−1 to 5.49 emu/g fo _r the LaFe _13-x-y Mn _x Si _y H _z alloys. The Magnetization versus magnetic field isotherms near transition temperature exhibited irradiation-induced magnetic hysteresis for the (MnNiSi) _1−x (Fe _2 Ge) _x (x = 0.34) while the LaFe _13-x-y Mn _x Si _y H _z samples did not result in any irradiation-induced magnetic hysteresis. In both the samples the magnitude of entropy change did not change due to irradiation however, the peak entropy change shifted to different temperatures in both the samples, (MnNiSi) _1−x (Fe _2 Ge) _x ( x = 0.34), showed a maximum entropy change, ΔS _mag of ∼ 11.139 J/kgK at 317.5 K compared to ΔS _mag of ∼ 11.349 J/kgK at T _ave peak of 312.5 K for the irradiated sample. LaFe _13-x-y Mn _x Si _y H _z , pristine sample exhibited a maximum magnetic entropy change, ΔS _mag ∼ 18.663 J/kgK, with the corresponding peak temperature, T _ave peak, of 295 K compared to ΔS _mag ∼ 18.736 J/kgK, at T _ave peak of 300 K. It was determined that irradiation applied to the samples did not induce any structural or magnetic phase changes in the selected compositions but rather modified the magnetic properties marginally.
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