The use of antiferromagnetic materials in spintronic devices has been proposed as an attractive alternative to ferromagnets, but only a few suitable materials are known. Here, the authors synthesize a new antiferromagnet (AFM)—tetragonal epitaxial CuMnAs—and show that it is ideal for spintronic applications.

/pdf/tetragonal-phase-of-epitaxial-room-temperature-zg2uvu4g39.pdf

Tetragonal phase of epitaxial room-temperature antiferromagnet CuMnAs

The electronic structure of delafossite type oxides AFeO2 (A = Ag, Cu) has been calculated using the full potential linearized augmented plane wave (FP-LAPW) method within the local spin density approximation (LSDA), Perdew−Burke−Ernzerhof (PBE-GGA), and Engel−Vosko (EV-GGA) generalized-gradient approximations. It was found that the EV-GGA provides a more realistic description of the electronic structure and the optical properties of AFeO2 than PBE-GGA or LSDA. The influence of electron correlations has been considered within the PBE-GGA+U and LSDA+U methods. The effective Hubbard U, Ueff, has been derived on the basis of an ab initio constraint calculation and by comparison with X-ray emission spectra. The energy band gap of AFeO2 within the PBE-GGA+U is found as a charge-transfer gap between O-2p to Fe-3d states. The theoretical optical band gaps Δ0 = 1.30, Δ1 = 2.06, and Δ2 = 3.20 eV for CuFeO2 are quite compatible with experimental data. We have predicted an optical band gap Δ0 = 1.90 eV for AgFeO2, a...

Electronic Structure and Optical Properties of AFeO2 (A = Ag, Cu) within GGA Calculations

We report physical properties of the conductive oxide PdCoO 2 in the layered delafossite structure through measurements of the electrical resistivity, specific heat, magnetic susceptibility, polari...

Roles of High-Frequency Optical Phonons in the Physical Properties of the Conductive Delafossite PdCoO2

We reinvestigated successive magnetic phase transitions ( T N1 ∼14.0 K, T N2 ∼10.5 K) in a frustrated triangular lattice antiferromagnet (TLA) CuFeO 2 by neutron diffraction measurements using single crystals. The magnetic structure of the intermediate-temperature phase between T N1 and T N2 is found to be a quasi -long range ordered sinusoidally amplitude-modulated structure with a temperature dependent propagation wave vector ( q q 0). These features of successive phase transitions are well explained by reinvestigated Monte-Carlo simulation of a 2D Ising TLA with competing exchange interactions up to 3rd neighbors, in spite of the Heisenberg spin character of orbital singlet Fe 3+ magnetic ions.

Partially Disordered Phase in Frustrated Triangular Lattice Antiferromagnet CuFeO 2

Neutron diffraction studies on a frustrated triangular lattice antiferromagnet (TLA) CuFeO 2 have been performed under an applied magnetic field up to 14.5 T. The first-field-induced state was foun...

Field-Induced Magnetic Phase Transitions in a Triangular Lattice Antiferromagnet CuFeO 2 up to 14.5 T

Magnetic ordering in a rhombohedrally stacked triangular lattice antiferromagnet, CuFeO 2 was investigated on powder and single crystals by measurements of neutron diffraction, magnetic susceptibility, Mossbauer effect together with Monte Carlo simulations. CuFeO 2 was found to exhibit transitions at T N1 =16±0.5 K and T N2 =11±0.5 K. The low temperature phase has an orthorhombic magnetic unit cell with collinear moments along the c -axis, whereas the intermediate temperature phase is a partially disordered phase with a monoclinic magnetic unit cell where 1/5 of moments remain paramagnetic. The Monte Carlo simulations for the Ising spin tiangular lattice antiferromagnet can reproduce the observed successive transition in the case of the exchange parameters 4 J 3 <2 J 2 ∼ J 1 <0. This combination of exchange parameters gives an account for the stability of the collinear magnetic structure in CuFeO 2 .

Tsukasa Sugino

Papers

Successive magnetic ordering in CuFeO2 : a new type of partially disordered phase in a triangular lattice antiferromagnet