Enhancement of the colossal magnetoresistance in [Eu.sub.1 - x] [Ca.sub.x] [B.sub.6]

• Published in: Journal of experimental and theoretical physics 2010-08, Vol.111 (2), p.246
• Main Authors: Glushkov, V.V, Anisimov, M.A, Bogach, A.V, Demishev, S.V, Dukhnenko, A.V, Kuznetsov, A.V, Levchenko, A.V, Samarin, N.A, Filippov, V.B, Churkin, O.A, Shitsevalova, N.Yu, Sluchanko, N.E
• Format: Article
• Language: English
• Subjects: Analysis; Electric properties; Magnetic fields; Magnetic properties; Solid solutions
• ISSN: 1063-7761; 1090-6509
• DOI: 10.1134/S1063776110080157

The transport and magnetic properties of single crystal samples of substitutional solid solutions [Eu.sub.1 - x] [Ca.sub.x][B.sub.6] (0 ≤ x ≤ 0.26) have been studied at temperatures 1.8-300 K in magnetic fields up to 80 kOe. It has been shown that an increase in the calcium concentration results in the suppression of the charge transport accompanied by an increase in the amplitude of the colossal magnetoresistance (CMR) up to the value (ρ(0) - ρ(H))/ρ(H) ≅ 7 x [10.sup.5] detected for x = 0.26 at liquid-helium temperature in a field of 80 kOe. The transition from the hole-like conductivity to the electron-like conductivity has been observed in the [Eu.sub.0.74][Ca.sub.0.26][B.sub.6] solid solution in the CMR regime at T < 40 K. The Hall mobility values [μ.sub.H] = 200-350 [cm.sup.2]/(V s) estimated for charge carriers in the strongly disordered matrix of the [Eu.sub.0.74][Ca.sub.0.26][B.sub.6] solid solution are comparable with the charge carrier mobility [μ.sub.H] = 400-600 [cm.sup.2]/(V s) for the undoped Eu[B.sub.6] compound. The anomalous behavior of the transport and magnetic parameters of the [Eu.sub.1 - x] [Ca.sub.x][B.sub.6] solid solutions is discussed in terms of a metal-insulator transition predicted within the double exchange model for this system with low carrier density.