The Effect of Fe Doping on the Magnetic and Magnetocaloric Properties of Mn_5−xFe_xGe₃

Abstract

The magnetic and magnetocaloric properties of a series of minutely doped Mn5-xFexGe3 compounds that exhibit the D88-type hexagonal crystal structure at room temperature have been investigated. For all Fe concentrations, the alloys are ferromagnetic and undergo a second-order ferromagnetic-to-paramagnetic transition near room temperature. Although the small Fe doping had little effect on the ferromagnetic transition temperatures of the system, changes in the saturation magnetization and magnetic anisotropy were observed. For x≤0.15, all compounds exhibit nearly the same magnetic entropy change of ~7 J/kg K, for a field change of 50 kOe. However, the magnitude of the refrigerant capacities increased with Fe doping, with values up to 108.5 J/kg and 312 J/kg being observed for field changes of 20 kOe and 50 kOe, respectively. As second-order phase transition materials, the Mn5-xFexGe3 compounds are not subject to the various drawbacks associated with first-order phase transition materials yet exhibit favorable magnetocaloric effects.

Magnetocaloric effect and critical behavior of the Mn5Ge3−xZnx alloys

“…Liu et al [23] found that the Curie temperature and isothermal magnetic entropy decrease as Ga content increase, while the magnetic moment reaches a maximum around x = 0.6 by studying the effect of Ga content in Mn 5 Ge 3−x Ga x on the MCE. Moreover, the magnetocaloric properties were previously researched for some Mn 5 Ge 3 -based off-stoichiometric alloys, such as Mn 5 Ge 3−x Ag x [24], Mn 5−x Co x Ge 3 [25], Mn 4.75 Ge 3 (Co, Fe) 0.25 [26], Mn 5−x Fe x Ge 3 [27], Mn 5+x Ge 3−x [28], Mn 5−x Ge 3 Ni x [29] and few others [30][31][32]. Although recent studies have reported magnetocaloric properties in these materials, a thorough study of the critical behavior near the phase transition temperature is indispensable for a better understand of the effect of doping on the MCE of the material.…”

Tuning of the Magnetocaloric Properties of Mn5Ge3 Compound by Chemical Modification

“…This compound, owing to its physical properties, may be used in magnetic refrigerators [39,40]. The attractive properties of Mn 5 Ge 3 initiated studies of, for example, off-stoichiometric Mn 5+x Ge 3-x alloys [41] or systems modified chemically by introducing elements such as Co [42][43][44][45], Fe [42,[44][45][46][47], or Ni [48] into the Mn position or by replacing Ge with Si [49,50], Ga [51], Sb [52], Al [53], Ag [54,55], or even Fe [56]. Moreover, simultaneous substitutions of Fe for Mn and Si for Ge have also been attempted [57,58].…”