Search

We present a microwave electron spin resonance study of the quantum spin dimer system TlCuCl3, which shows the magnetic-field-induced ordering with both antiferromagnetic spin order and ferroelectricity by the Bose-Einstein condensation (BEC) of triplon quasiparticles. Our main achievement is an electrical switching of the nonreciprocal directional microwave response in the triplon BEC phase. High-speed directional control of microwave absorption by applying an electric field has been accomplished in this Letter. The strength of the observed nonreciprocal microwave response well agrees with the calculation based on Kubo theory with the parameters, evaluated from the static electric polarization in this material. [ABSTRACT FROM AUTHOR]

We measured the temperature dependence of the magnetic susceptibility and specific heat and the magnetic-field dependence of the magnetization of CuInVO5. An antiferromagnetically ordered state appears below TN = 2.7 K. We observed a 1/2 quantum magnetization plateau above 30 T at 1.3 K. We consider that the probable spin model for CuInVO5 is an interacting spin-1/2 tetramer model. We evaluated values of the intratetramer interactions as J1 = 240±20 K (antiferromagnetic) and J2 = -142±10 K (ferromagnetic). The ground state of the isolated spin tetramer with the J1 and J2 values is spin singlet. The shrinkage of ordered magnetic moments by quantum fluctuation can be expected. Detectable low-energy longitudinal-mode magnetic excitations may exist in CuInVO5. [ABSTRACT FROM AUTHOR]

We performed inelastic neutron scattering experiments on Cu2114Cd11B2O6 powder. The magnetic excitations at low temperatures are similar to those of the interacting spin-1/2 tetramers in the ordered state. The weak excitations existing above 3 meV suggest that the Higgs mode appears in Cu2CdB2O6 at ambient pressure and zero magnetic field. We evaluated J1=27.3±1.0 and J2=-14.0±1.4 meV for the intratetramer interactions and J3=-0.4±0.2 and J4=1.4±0.2meV for the intertetramer interactions. The spin gap in the isolated spin tetramer was calculated to be 1.6 meV, which is less than the effective intertetramer interaction value (3.6±0.8 meV). Therefore, antiferromagnetic long-range order is possible, although the ground state of the isolated spin tetramer is the spin-singlet state. We discuss the temperature dependence of the magnetic excitations. [ABSTRACT FROM AUTHOR]

We measured the temperature dependence of the magnetic susceptibility χ(T) and the specific heat C(T) and the magnetic-field dependence of the magnetization M(H) of A2Ni2Mo3O12(A = Rb or K) powder. We consider that the probable spin model is an interacting spin-1 antiferromagnetic tetramer model. We evaluated values of the intratetramer interactions as J1=9 K and J2=18 K, and the effective intertetramer interaction as Jeff=4 K for Rb2Ni2Mo3O12. The susceptibility and magnetization at 1.3 K of K2Ni2Mo3O12 are very close to those of Rb2Ni2Mo3O12. We observed a phase transition to a magnetically ordered state in C(T)/T in magnetic fields above 3 T. The transition temperature increases with magnetic field. Probably, the ordered state appears around 1.8 K even in 0 T. The ordered state in 0 T, however, is not stable enough like an order in the vicinity of a quantum critical point. Longitudinal-mode magnetic excitations may be observable in single crystalline A2Ni2Mo3O12(A = Rb or K). [ABSTRACT FROM AUTHOR]

We measured magnetization, specific heat, electron spin resonance, neutron diffraction, and inelastic neutron scattering of CrVMoO7 powder. An antiferromagnetically ordered state appears below TN=26.5±0.8 K. We consider that the probable spin model for CrVMoO7 is an interacting antiferromagnetic spin-3/2 dimer model. We evaluated the intradimer interaction J to be 25±1 K and the effective interdimer interaction Jeff to be 8.8±1 K. CrVMoO7 is a rare spin dimer compound that shows an antiferromagnetically ordered state at atmospheric pressure and zero magnetic field. The magnitude of ordered moments is 0.73(2)μB. It is much smaller than a classical value ~3μB. Longitudinal-mode magnetic excitations may be observable in single crystalline CrVMoO7. [ABSTRACT FROM AUTHOR]