Percolation and the colossal magnetoresistance of Eu-based hexaboride

• Published in: Physical review letters Vol. 93; no. 14; pp. 147203.1 - 147203.4
• Main Authors: WIGGER, G. A, BEELI, C, FELDER, E, OTT, H. R, BIANCHI, A. D, FISK, Z
• Format: Journal Article
• Language: English
• Published: Ridge, NY American Physical Society 01-10-2004
• Subjects: Colossal magnetoresistance; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetotransport phenomena, materials for magnetotransport; Physics; Electrical conductivity; Magnetization; Europium Borides; Calcium Borides; Electron-phonon interactions; Colossal magnetoresistance; Rare earth compounds; Defects; Specific heat; Phase separation; Sublattices; Percolation; Chemical composition
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.93.147203

Upon substituting Ca for Eu in the local-moment ferromagnet EuB6, the Curie temperature T(C) decreases substantially with increasing dilution of the magnetic sublattice and is completely suppressed for x<or=0.3. The Ca substitution leads to significant changes of the electronic properties across the EuxCa1-xB6 series. Electron microscopy data for x approximately 0.27 indicate a phase separation into Eu- and Ca-rich clusters of 5 to 10 nm diameter, leading to percolation-type phenomena in the electrical transport properties. The related critical concentration x(p) is approximately 0.3. For x approximately 0.27, we observe colossal negative magnetoresistance effects at low temperatures, similar in magnitude as those reported for manganese oxides.