Magnetism and electronic structure of the (Co1−xMnx)2P system

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Abstract

For (Co1−xMnx)2P compounds (x=0.6 and 0.65) both X-ray diffraction (from 100 to 420 K) and χac(T) and MT(H) measurements under pressure up to 1.5 GPa were analysed. The electronic structure was computed using the KKR–CPA method. Changing the Mn content from x=0.5–0.65 enhances significantly the DOS near the Fermi energy EF.

Introduction

The solid solution system (Co1−xMnx)2P crystallises in two crystal structures: orthorhombic which is of Co2P-type (SG: Pnma) for 0<x<0.8 and hexagonal which is of Fe2P-type (SG:P6̄2m) for x>0.8. In the range 0<x<0.5, manganese substitutes on the P-pyramidal site only, while for higher Mn contents i.e. x>0.5, it substitutes on the T-tetrahedral site. Compounds with x<0.6 all exhibit a ferromagnetic (F) character, then a metamagnetic (M) behaviour is observed for Mn contents 0.6<x<0.8 below the temperature of a tricritical point which was found at T=200 K for x=0.63. When the Mn content is higher than 0.8, only antiferromagnetic (AF) characteristics are observed [1], [2].

Section snippets

Experimental

For x=0.6 and 0.65, X-ray diffraction patterns were recorded in the 100–420 K temperature range, using a Philips diffractometer (λCuKα). The AC susceptibility and magnetisation were measured under hydrostatic pressure in the temperature range 80–420 K. TC the Curie temperature and TMF the M–F transition temperature were deduced at various pressures from the temperature dependence of the AC susceptibility. The magnetisation measurements were performed in pulsed magnetic fields up to 3 T and under

Results and discussion

X–ray diffraction measurements were performed on the (Co1−xMnx)2P system (x=0.6 and 0.65) at different temperatures in order to check the magnetoelastic properties of the system. The Fullprof program (profile type) was used to determine both the unit cell and the atom parameters (Table 1). Jumps of the unit cell parameters and volume were found both at TMF and TC as seen in Fig. 1.

(P,T) magnetic phase diagrams for (Co1−xMnx)2P system (x=0.6 and 0.65) were built from the temperature dependence

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