Robustness of helical magnetic structure under external pressure in Fe-doped MnNiGe alloy

TL;DR

This study explores how external pressure influences the magnetic helical structure of Fe-doped MnNiGe alloy, revealing pressure-induced changes in magnetic ordering and propagation vectors through neutron diffraction analysis.

Contribution

It provides new insights into pressure effects on magnetic structures in Fe-doped MnNiGe, highlighting the stabilization and temperature dependence of incommensurate magnetic propagation vectors.

Findings

External pressure lowers the martensitic transition temperature.

Pressure alters the incommensurate magnetic propagation vector.

Magnetic structure stability is affected by external pressure.

Abstract

We have investigated the detailed magnetic structure of a Fe-doped MnNiGe alloy of nominal composition MnNi$_{0.75}$Fe$_{0.25}$Ge by ambient and high pressure (6 kbar) neutron powder diffraction study. The alloy undergoes a martensitic phase transition between 230 K and 275 K. The low-temperature martensite phase orders antiferromagnetically with helical modulation of Mn-spins. At 1.5 K, the incommensurate propagation vector $\bf k$ is found to be (0.1790(1),0,0), and it remains almost unchanged with temperature under ambient condition. The Application of external pressure ($P$) reduces the martensitic transition temperature and results in a significant change in the incommensurate magnetic propagation vector. At 10 K, with 6 kbar of external pressure, the incommensurate magnetic structure of the alloy stabilizes with $\bf k$ = (0.1569(1),0,0). Interestingly, the strong temperature dependence of $\bf k$ in the presence of external $P$ has also been observed.