On the instability of the giant direct magnetocaloric effect in CoMn0.915Fe0.085Ge at. % metamagnetic compounds

Abstract

The giant magnetocaloric effect was quantified in CoMn 1-x Fe x Ge (x = 0.085–0.12) nom. at. % polycrystals across the high temperature hexagonal (P6 3 /mmc) to low temperature orthorhombic (Pnma) phase transition via differential scanning calorimetry (DSC) and multiple (thermo) magnetization measurements. It was found that increasing Fe content led to the decrease of both the martensitic transformation temperature and entropy change ( ) at the point of the phase transition. Moreover, first-time magnetocaloric measurements resulted in irreproducible entropy change versus temperature diagrams, which was attributed to the release of internal pressure in bulk samples that disintegrated into powder upon transformation. CoMn 1-x Fe x Ge demonstrated larger magnetic field-induced entropy changes and giant magnetocaloric effect (MCE) compared to other CoMnGe alloys doped with Si, Sn, Ti, and Ga. However, the observed brittleness and apparent change in volume at the magnetic transition was posited to influence the material’s potential for regenerative applications.

Large magnetocaloric effect near room-temperature by tuning the magneto-structural transition in (Mn, Fe)(Ni, Fe)Si alloy

“…Recent studies on equiatomic alloys (having the general formula M-M′-X, where M & M′ are transition metals and X is the main group element) show that all the stoichiometric compounds undergo a structural transition from orthorhombic crystal symmetry to hexagonal crystal symmetry in the high-temperature region apart from the low-temperature magnetic transition [6][7][8][9][10][11][12][13][14][15][16]. So, in these types of alloys, coupling of the magnetic transition with the structural phase transition is necessary to achieve large MCE due to the large magnetization difference (ΔM) around the transition region [17,18].…”

Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys

“…It always displays an FM state in the low-temperature range. T M in MnCoGe-based alloys is sensitive to the composition; therefore, element substitution is widely utilized by substituting one of the three basic constituents in small amounts [20][21][22][23][24][25][26][27][28][29]. The desired goal of having large magnetoresponsive behaviors (e.g.…”