反強磁性金属CeRh₂Si₂のsingle-qとmulti-q秩序相の面内異方性

抄録

We performed magnetization, resistivity, and neutron diffraction measurements under uniaxial stress applied along [1-10] direction on the tetragonal magnet CeRh₂Si₂ with commensurate magnetic orders. CeRh₂Si₂ has two successive antiferromagnetic (AF) orders in zero magnetic field. The high temperature phase (AF1 phase) has the magnetic modulation wave vector of q = (1/2, 1/2, 0), and the low temperature phase (AF2 phase) is characterized by the four q-vectors of q = (1/2, ±1/2, 0), and (1/2, ±1/2, 1/2). By measuring the uniaxial stress dependence, we confirmed that the AF1(AF2) phase has the single-q(multi-q) magnetic order with two-fold(four-fold) rotational symmetry. We also performed inelastic neutron scattering measurement on the single crystal samples. We found a magnetic excitation at the transfer energy ħω ∼ 8 meV. By applying the linear spin-wave theory, we found that the nearest and the next-nearest neighbor exchange interactions on the ab-plane, J₁ and J₂, are dominant in the AF2 phase. However, the J₁-J₂ model cannot lift the degeneracy between the single-q (AF1) and multi-q (AF2) phases. We suggest that it can be lifted by taking into account the biquadratic interaction derived from the perturbative expansion for the Kondo lattice Hamiltonian[10].