High-field magnetization of Heusler compound ${\mathrm{Fe}}_2{\mathrm{Mn}}_{1-x}{\mathrm{V}}_x\mathrm{Si}$

${\mathrm{Fe}}_2\mathrm{MnSi}$ exhibits a ferromagnetic transition at $T_C\sim 230$ K and another transition to a phase with antiferromagnetic components at $T_A\sim 60$ K. By substituting V for Mn, so as to obtain ${\mathrm{Fe}}_2{\mathrm{Mn}}_{1-x}{\mathrm{V}}_x\mathrm{Si}$, $T_A$ is revealed to decrease with $x$ and then vanish around $x\sim 0.2$. In this study, the phase boundary of the transition at $T_A$ in the high-field range is found for $0\le x\le 0.15$ with pulsed fields up to $\sim 70$ T. The magnetization of ${\mathrm{Fe}}_2{\mathrm{Mn}}_{1-x}{\mathrm{V}}_x\mathrm{Si}$ slowly increases even at the highest field of $\sim 70$ T, though it occurs more gradually as $x$ increases. We compare the magnetization for $0\le x\le 0.20$ at 62 T with the Slater-Pauling rule, which holds when a Heusler compound is a half-metal, and find fairly good agreement. This suggests an intimate relation between the high-field phase and the half-metallic electronic structure, and that at the high-field limit the phase approaches the half-metallic state, which has been predicted by band-structure calculations.

Figure 1

(a) Magnetization versus magnetic field $M\left(B\right)$ for ${\mathrm{Fe}}_2{\mathrm{Mn}}_{0.95}{\mathrm{V}}_{0.05}\mathrm{Si}$ at up to 63 T in an expanded scale. In the inset, $M\left(B\right)$ over the entire magnetic field range is shown. (b) Values from the derivative $dM/dB$. The arrows show the transitions.

Figure 2

Magnetization versus magnetic field $M\left(B\right)$ for ${\mathrm{Fe}}_2{\mathrm{Mn}}_{0.85}{\mathrm{V}}_{0.15}\mathrm{Si}$ at up to 63 T in an expanded scale. In the inset, the derivative $dM/dB$ is shown. The arrow shows the transition.

Figure 3

Transitions between the AF and F phases. Open symbols show the transitions determined from the measurements using SQUID and solid symbols show those obtained using pulsed magnets.

Figure 4

Magnetization versus magnetic field $M\left(B\right)$ for ${\mathrm{Fe}}_2{\mathrm{Mn}}_{1-x}{\mathrm{V}}_x\mathrm{Si}$ ($x=0$, 0.05, 0.1, 0.15, and 0.2) up to 72 T (63 T) at 4.2 K. The broken lines show examples of extrapolations.

Figure 5

Plot of the magnetizations at $T=4.2$ K under $B=1$ T as a function of $x$ for ${\mathrm{Fe}}_2{\mathrm{Mn}}_{1-x}{\mathrm{V}}_x\mathrm{Si}$ (crosses) from Kawakami [17]. In this case, the measured magnetization can be seen as the saturation magnetization for the ferromagnetic state, while the magnetizations at $T=4.2$ K under $B=62$ T are the present measurements (open circles). The solid line follows the Slater-Pauling rule, which holds when Heusler compounds are half-metals.