Giant exchange bias in Mn2FeGa with hexagonal structure

Abstract

In this study, we present the experimental observation that polycrystalline Mn2+xFe1−xGa (x = −0.2, 0, 0.2, 0.4) compounds can be synthesized to be D019-type (Ni3Sn-type) hexagonal structure with space group P63/mmc. A giant exchange bias field up to 1.32 kOe was achieved in hexagonal Mn2FeGa alloy at 5 K. A cluster glass state is confirmed by ac susceptibility measurement under different driving frequencies. Interestingly, robust horizontal and vertical shifts in magnetic hysteresis loop were simultaneously observed at 5 K under high cooling field up to 90 kOe. The large exchange bias is originated from the large exchange anisotropy between cluster glass phase and ferrimagnetic matrix. The vertical shift is thought to be attributed to the incomplete reversal of frozen cluster spins.

Large exchange bias in magnetic shape memory alloys by tuning magnetic ground state and magnetic-field history

“…Moreover, weak FM interactions may also exist in the martensitic state [40], which give rise to the formation of many FM clusters coexisting with the surrounding AFM matrix. Owing to the spin frustration caused by the inherent competition between FM and AFM interactions, these FM clusters undergo a freezing transition into the SG state below T p [19,27,30].…”

“…−zv [27,30]. In this formula, τ is the relaxation time of locally correlated spins and equals (2πf) −1 (f is the frequency); τ 0 , T g , and zv are the microscopic relaxation time, the SG transition temperature, and the dynamic critical exponent, respectively.…”

“…The EB measurement follows a two-step protocol: i) cooling from a high temperature to the desired testing temperature under a constant magnetic field (H FC ), i.e., the field cooling (FC) process; ii) a subsequent isothermal magnetization process by sweeping a magnetic field to the maximum value (H Max ). Many investigations have demonstrated that the unidirectional anisotropy can be established below a blocking temperature during the FC process [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. On the other hand, in some Ni-Mnbased MSMAs, the unidirectional anisotropy can also be isothermally created by applying a sufficiently large H Max after a zero-field cooling (ZFC) process [32][33][34][35].…”

Tailoring structural and magnetic properties of Mn3−x Fe x Ga alloys towards multifunctional applications

“…The rich magnetic properties of hexagonal Mn 3Àx Fe x Ga alloys, including the non-collinear and collinear magnetism, result in many useful functional properties, i.e. the topological Hall effect in Mn 3 Ga and exchange bias in Mn 2 FeGa (Liu et al, 2016). This means these alloys possess great potential for technological applications.…”

“…Mn 1.5 Fe 1.5 Ga and Mn 1.8 Fe 1.2 Ga alloys (Nayak et al, 2015). In previous work, we presented our experimental observation of a D0 19 -type hexagonal structure and an accompanying large exchange-bias effect in a polycrystalline Mn 2 FeGa alloy when subjected to suitable heat treatment (Liu et al, 2016).…”