Giant magnetic anisotropy in Li$_{3-x}$Fe$_x$N permanent magnets

ORAL

Abstract

Single crystals of Li$_2$(Li$_{1-x}$Fe$_x$)N were successfully grown out of Li-flux. Fe-concentrations and lattice parameters were determined by means of single crystal and powder diffraction which also confirmed the substitution of Fe on only one of the Li sites resulting in Li$_{1-x}$Fe$_x$ layers separated by Li$_2$N layers. Magnetization measurements revealed a ferromagnetically ordered ground state with Curie temperatures of $\sim 60$\,K for Fe concentrations of $x \approx 20$\%. Large saturation moments of up to 5\,$\mu_B$ per Fe atom were found along the hexagonal crystallographic $c$-axis. These values exceed the spin-only contribution of Fe and are also reflected in correspondingly large effective moments at room temperature. The anisotropy field at $T = 2$\,K, defined as intersection of the magnetization for $M \parallel c$ and $M \perp c$, can be estimated to lie well beyond 100 Tesla. Electrical resistivity measurements show insulating behavior and raise questions about the nature of the underlying magnetic exchange mechanism.

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Authors

  • Anton Jesche

    The Ames Laboratory, Iowa State University, Ames, USA

  • Srinivasa Thimmaiah

    The Ames Laboratory, Iowa State University, Ames, USA

  • Sergey Bud'ko

    The Ames Laboratory, Iowa State University, Ames, USA, Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames Laboratory, US DOE, Iowa State University, Department of Physics, Iowa State University, Ames Laboratory, US DOE, and Dept. of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA

  • Paul Canfield

    Ames Laboratory and Iowa State University, The Ames Laboratory, Iowa State University, Ames, USA, Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames Laboratory, US DOE, Iowa State University, Department of Physics, Iowa State University, Iowa State University