Percolation and Colossal Magnetoresistance in Eu-based Hexaborides

Abstract

Upon substituting Ca for Eu in the local-moment ferromagnet EuB${}_6$, the Curie temperature $T_C$ decreases substantially with increasing dilution of the magnetic sublattice and is completely suppressed for $x$ $\le$ 0.3. The Ca substitution leads to significant changes of the electronic properties across the Eu${}_x$Ca${}_{1-x}$B${}_6$ series. Electron microscopy data for $x$ $\approx$ 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 $x$ $\approx$ 0.27, we observe colossal negative magnetoresistance effects at low temperatures, similar in magnitude as those reported for manganese oxides.

4 pages, 5 figures, submitted to PRL

References in corpus (2)

• Resistivity of Mixed-Phase Manganites
• Electronic transport in EuB${}_6$

Cited by in corpus (9)

• Magneto-optical evidence of double exchange in a percolating lattice
• Gradual transition from insulator to semimetal of Ca${}_{1-x}$Eu${}_x$B${}_6$ with increasing Eu concentration
• Anomalous magnetoresistance of EuB${}_{5.99}$C${}_{0.01}$: Enhancement of magnetoresistance in systems with magnetic polarons
• Magneto-optical behaviour of EuIn_2P_2
• Field-controlled phase separation at the impurity-induced magnetic ordering in the spin-Peierls magnet CuGeO3
• Incommensurate broken helix induced by nonstoichiometry in the axion insulator candidate EuIn${}_2$As${}_2$
• Signatures of electronic phase separation in the Hall effect of anisotropically strained La0.67Ca0.33MnO3 films
• Concurrent Magnetic and Metal-Insulator Transitions in (Eu,Sm)B_6 Single Crystals
• Anderson Localization Triggered by Spin Disorder---with an Application to Eu_x Ca_1-x B_6