Correlation between the electric and conical-uniaxial ferromagnetic phase transitions in the metallic spinel CuCr2Se4

• Published in: Physica Status Solidi (b) Vol. 243; no. 3; pp. 738 - 745
• Main Authors: Tokiwa, N., Hidaka, M.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.03.2006; WILEY‐VCH Verlag; Wiley
• Subjects: 72.15.Eb; 72.15.Gd; 72.25.Dc; 72.80.Ga; 75.50.Dd; 75.50.Ee; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity phenomena in semiconductors and insulators; Electronic transport in condensed matter; Exact sciences and technology; Galvanomagnetic and other magnetotransport effects; Magnetic properties and materials; Nonmetallic ferromagnetic materials; Physics; Studies of specific magnetic materials; Double exchange; Metallic conduction; Chromium selenides; Magnetization; Magnetic field effects; Magnetic transitions; Heat treatments; Copper selenides; Temperature effects; Spinels; Ferromagnetism; Magnetoresistance; Semiconductor metal transition
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200541160

The electric resistivity in CuCr2Se4 has been measured below room temperature under applied magnetic fields (H ) up to 1.0 T in the metallic ferromagnetic phase, in addition to magnetization measurements. The temperature dependence of the electric resistivity (ρ ) shows an electric phase transition at about 65 K (T e) and a different linearity of ρ –T curves in the regions of T < 60 K and T > 100 K. Both regions are metallic, while in the intermediate region 60 K < T < 100 K a semiconductor‐like state occurs. The T e transition temperature slightly decreases from about 65 K to 59 K on increasing the magnetic field. The magnetoresistance (MR) shows a crossover to a positive value or a negative one below and above T e, though the MR–T curves depend on the magnetic fields. The magnetization curves deviate from a tentative Brillouin function at about 65 K (H = 50 G), 200 K (H = 400 G), 230 K (H = 800 G) and 170 K (H = 0.2 T), and a weak modulation at about 65 K to 70 K (T 1) under the magnetic fields. It is suspected that the magnetic transition occurring at T 1 is from a conical to a uniaxial ferromagnetic state on heating. The T e electric transition results from a slight change of a Zener band situation, which is induced by a spin‐dependent double‐exchange interaction at T 1. The intermediate semiconductor‐like state is between two different Zener band situations in the conical and uniaxial ferromagnetic states, which are both metallic. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)