Wide temperature span of entropy change in first-order metamagnetic MnCo1−xFexSi

Abstract

The crystal structure and magnetic properties of MnCoxFe1−xSi (x = 0–0.5) compounds were investigated. With increasing Fe content, the unit cell changes anisotropically and the magnetic property evolves gradually: Curie temperature decreases continuously, the first-order metamagnetic transition from a low-temperature helical antiferromagnetic (AFM) state to a high-temperature ferromagnetic state disappears gradually and then a spin-glass-like state and another AFM state emerge in the low-temperature region. The Curie transition leads to a moderate conventional entropy change. The metamagnetic transition not only yields a larger negative magnetocaloric effect at lower applied fields than in MnCoSi but also produces a very large temperature span (103 K for Δμ0H = 5 T) of ΔS(T), which results in a large refrigerant capacity. These phenomena were explained in terms of crystal structure change and magnetoelastic coupling mechanism. Because of the large isothermal entropy change, the wide working temperature span and the low cost, MnCo1−xFexSi compounds are promising candidates for near room-temperature magnetic refrigeration applications.