Structural and magnetic phase transitions in CoxNi1−xMnGe system under pressure

The magneto-structural transition in Mn1−xFexCoGe

“…For pure MnCoGe, a TiNiSi-type orthorhombic structure (Pnma) is formed from the Ni2In-type hexagonal structure (P63/mmc) through a martensitic transformation at TM, determined as ~398 K to ~458 K by Johnson [19] or ~650 K by Kanomata et al [20], with a Curie temperature TC orth ~345 K [21]. Importantly, the martensitic transformation temperature TM can be tuned easily [12,[22][23][24]. Slight compositional changes, achieved via doping for example [25,26], can stabilise the hexagonal phase to low temperature with a ferromagnetic transition occurring in the hexagonal phase at the Curie temperature TC hex ~275 K [27].…”

Hydrostatic pressure tuned magneto-structural transition and occurrence of pressure induced exchange bias effect in Mn0.85Fe0.15NiGe alloy

“…[13][14][15] Recent investigation on the Fe-doped MnNiGe alloy (Fe doping both in Mn and Ni sites of the alloy) by Liu et al indicates the presence of ferromagnetic (FM) and SG-like ground state in the system. 8 Fe doping at the Mn site of the MnNiGe layered compound not only breaks the spiral antiferromagnetic (AFM) Mn-Ge-Mn inter-layer interaction but also induces FM interaction between Mn atoms of the same layer by reducing lattice volume of the alloy.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] Among various members of MEAs, MnNiGe is one of the potential candidates which undergoes a first-order diffusionless structural phase transition, known as martensitic phase transition (MPT), at 470 K during cooling and orders spiral antiferromagnetically below 346 K. 1,3,4,8 Physical and chemical pressures are the two most influencing parameters that can affect the physical properties of these materials simply by modifying structural parameters like lattice volume, bond angle etc. 8,13,14 Among these two, chemical pressure approach (different doping studies) is much popular among the researchers due to easy sample preparation and measurement options. However, the purest form of perturbation can only be given by the physical pressure approach.…”

Magnetocaloric effect and magnetostructural coupling in Mn0.92Fe0.08CoGe compound

“…Importantly, the value of T str depends strongly on several factors including: external pressure, 8 the vacancies in the Co and Mn sites, as well as variation in chemical environment due to element substitution on Mn, Co, or Ge sites. [9][10][11][12][13][14][15][16][17] Recently, MnCoGebased compounds have attracted significant attention; [9][10][11][12][13][14][15][16][17] this is due mainly to the strong coupling between magnetism and structure in these materials.…”

“…Stoichiometric MnCoGe has an orthorhombic TiNiSitype structure (space group Pnma) at low temperatures (below $650 K) and exhibits a martensitic structural transformation 8 from the low-temperature orthorhombic TiNiSitype structure to a high-temperature hexagonal Ni 2 In-type structure (space group P63/mmc) around T str ¼ 650 K. The MnCoGe compounds in both structural states are ferromagnets but their magnetizations and Curie temperatures (T C ) differ considerably (T C ¼ 345 K for the orthorhombic structure, T C ¼ 275 K for the hexagonal structure). Importantly, the value of T str depends strongly on several factors including: external pressure, 8 the vacancies in the Co and Mn sites, as well as variation in chemical environment due to element substitution on Mn, Co, or Ge sites.…”