0000000000061640
AUTHOR
B. Dorner
Magnetic excitations of the singlet ground state antiferromagnet CsFeBr3 in a magnetic field
Abstract The magnetic excitations in the quasi-one-dimensional singlet ground state antiferromagnet CsFeBr3 have been studied by inelastic neutron scattering in the presence of an applied magnetic field, H‖c and H⊥c. With H‖c, the dispersion curves renormalise so that the exchange interaction has a decreasing influence with increasing field. H⊥c has little or no effect on the dispersion of the magnetic excitations.
Study of the Spin Wave Linewidth in a 1-D Easy-Plane Ferromagnet Using Neutron Polarization Analysis
An anomalous wavevector dependence in the spin wave linewidth associated with fluctuations out of the easy plane is observed for the first time in the one-dimensional easy-plane ferromagnet CsNiF3 by means of inelastic polarized neutron scattering. The linewidths of the spin waves, one attributed to spin fluctuations out of the easy plane and another in the easy plane, are studied separately throughout the Brillouin zone. The zone boundary narrowing of the linewidth associated with the spin fluctuations in the easy plane is observed for the first time in agreement with the classical spin wave theory. The deviations from the classical result at large qc and high temperature are interpreted a…
Inelastic neutron scattering measurements on Nd2Fe14B and Y2Fe14B single crystals
Abstract Inelastic neutron scattering measurements have been carried out on Nd 2 Fe 14 B and Y 2 Fe 14 B single crystals. Temperature dependent acoustic magnon dispersion curves have been found along the high-symmetry directions [0,0,1] and [1,0,0] with a gap at (0,0,2). Soft mode behaviour at spin wave vector q = 0 was observed for Nd 2 Fe 14 B near the spin reorientation temperature. The inelastic scattering intensity decreases steeply for larger q . Therefore, the dispersion curves could be measured until the middle of the Brillouin zone only. The experimental results are discussed in the frame of a classical spin wave model.
Magnetic excitations and phase transition of CsFeBr3 in an external magnetic field
In CSFeBr3 the Fe2+ ion with effective spin one has locally a singlet ground state (m=0). The antiferromagnetic interactions between neighbouring Fe-ions are too weak as compared with the anisotropy constant to introduce long range order in the absence of an external field. By inelastic neutron scattering we studied the magnetic excitations in an external magnetic field up to 5 Tesla applied along thec-axis. A linear Zeeman splitting was observed with a Lande factorg=2.4. The field renormalizes the dispersion curves in such a way that the exchange interaction has decreasing influence with increasing field. Theoretical calculations according to the excitonic model of Lindgard describe the ex…
Magnetic field and temperature dependent correlations in the singlet ground state system CsFeBr3
Abstract In the singlet ground state system CsFeBr 3 the temperature and magnetic field dependence of the magnetic dispersion curves have been measured by inelastic neutron scattering. At a field of 4.1 T magnetic Bragg peaks appear at (⅓ ⅓ 1) and (⅔ ⅔ 1). The correlation lengths were derived from the experimental data by integrating the constant Q -scans over the energy transfer. The Q -dependence was fitted to Lorentzians and correlations lengths were extracted for different directions in the lattice. These correlation lengths decrease with increasing temperature and increase with increasing field. Above the phase transition the correlation lengths decrease again.
Temperature and magnetic field dependent correlations in the singlet ground state system CsFeBr3
The magnetic excitations in CsFeBr3 have been measured with inelastic scattering of cold neutrons to high precision at 80 mK. The fact that the lowest frequency mode softens with decreasing temperature but stabilizes at 0.11 THz below 2.5 K is the indication that CsFeBr3 remains a SGS system forT→0. From dispersion curves measured earlier in a magnetic field along the chain axis experimental intensities were derived and in turn correlation lengths. Correlation lengths were also calculated using the new parameters for exchange and anisotropy. The experimental results and the calculations both show that the correlation lengths increase for increasing magnetic field, flatten off around the pha…