Neutron diffraction, magnetic and superconducting measurements on vanadium–manganese–gallium alloys

Abstract

Eleven alloys from the binary and ternary range (VMn)2Ga5 have been investigated using neutron powder diffraction methods supported by measurements of magnetic susceptibility and superconducting transition temperatures. A magnetic structure is present in alloys in the composition range around (Mn0.2 V0.s)2 Gas to Mn2Gas. The magnetic moment found in the alloy Mn2Ga5 increases on the addition of vanadium to a maximum around the composition (Mn0.sV0.2hGas. It then decreases and disappears around the composition (Mn0.2V0.8)2Gas. Possible changes in the magnetic structure are suggested in order to account for this. There is some evidence of weak superconductivity in the alloy V2Gas. This disappears on the addition of manganese.

Two-Dimensional Superdegeneracy and Structure−Magnetism Correlations in Strong Ferromagnet, Mn2Ga5

“…Figure a shows the magnetization of the Mn 2 Ga 5 in the temperature region from 1.8 to 600 K. The temperature region above 600 K did not show any noticeable change in the magnetization up to 800 K, the maximum temperature in our measurement. The onset of a ferromagnetic transition is found at ∼450 K, which is significantly lower than what was found for the Mn-deficient compound . Below 450 K, the magnetic moment gradually reaches 2.71 μ B per formula unit as the temperature decreases.…”

“…However, the single-crystal structure of the Mn 2 Ga 5 has not been available yet for the details of the structure and for the studies of its magnetism. More critically, the reported magnetism of the Mn 2 Ga 5 was in fact from a significantly Mn-deficient sample, Mn 1.85 Ga 5 ( T c = 521 K), indicating a possible phase width, but the existence of a stoichiometric compound itself has to be confirmed.…”

“…The title compound, Mn 2 Ga 5 , is quite intriguing in this regard, as it is known to show a strong ferromagnetism even at room temperature and exhibits a magnetic moment of 1.78 μ B /Mn based on neutron diffraction studies. , In fact, the gallide is the only ferromagnetic compound that is thermodynamically stable in the Mn−Ga binary system. The known Mn-richer compounds are either ferrimagnetic or antiferromagnetic, except the metastable δ-MnGa. − Both of other known Ga-rich compounds, MnGa 4 and MnGa 3 , are Pauli-paramagnetic, being consistent with the aforementioned behavior of the p-metal-rich transition metal intermetallics.…”