MAGNETIC FIELD PHASE DIAGRAM OF THE NON-CUBIC ANTIFERROMAGNETIC Mn5Si3

R.F. LUCCAS; A. CORREA-ORELLANA; F. J. MOMPEAN; M. GARCÍA- HERNANDEZ; H. SUDEROW

Miraflores de la Sierra

Congreso; International Workshop Advances in nanostructured superconductors: materials, properties and theory; 2014

Transition metal magnets are characterized by having moments strongly linked to their local environment. This leads to a rich interplay between d-electron magnetism and nearest-neighbor interactions.[1] MnSi and MnGe crystallize in a cubic structure without center of inversion, leading to spiral magnetic order. The compound Mn5Si3 is antiferromagnetically ordered at low temperatures. Previous neutron scattering in polycrystalline or powder samples show several magnetic phases, with two magnetic transitions TN1 = 60 K and TN2 = 90 K. Below TN1 , spins are arranged in a non-collinear structure, showing local chirality. This phase is destroyed by a magnetic field of several Tesla, favoring the high temperature antiferromagnetic arrangement.[2] Here we have synthesized crystals of Mn5Si3 out of Cu flux. We obtain needles with typically 6 mm in length and cross section of about 1 mm2 with a non-regular octagonal section. We find, from magnetization measurements up to 7 T and down to 2K performed on individual needles along their long axis, that there are actually three magnetic phases, with an additional transition at TN 1* = 45 K. Contrary to results in other polycrystalline samples, we find that TN1 is magnetic field independent, whereas TN 1* strongly decreases with the magnetic field, and presents transitions when increasing field at a fixed temperature. Our measurements suggest that the low temperature magnetic non‐collinear structure unwinds with the magnetic field through metamagnetic transitions. There is an additional intermediate magnetic phase between 45 K and 60 K, which is probably also non-collinear. The role of sample synthesis on the magnetic structure is briefly discussed.