Far-Infrared Laser Study of Magnetic Resonance in DyPO4

Abstract

Magnetic resonance has been observed in the Ising system, DyPO₄, utilizing a unique far‐infrared laser‐magnetic resonance spectrometer. Spectra were obtained at 220.23 μ (45.407 cm⁻¹) and 171.67 μ (58.25 cm⁻¹) at 4.2°K in applied fields (H_∥C) sufficient to saturate the spin system. The radiation source was a pulsed‐discharge gas laser (using H₂O or D₂O). The spectrometer employed a 90‐kOe superconducting solenoid and a dual‐beam detection system which electronically integrates the pulsed signals and records directly the percentage transmission. The resonance yields three super‐imposed hyperfine patterns, due to even isotopes (I = 0); Dy(161) and Dy(163) both ($\mathrm{I=}\frac{5}{2}$ ). All six lines of Dy(163) were resolved yielding a spin Hamiltonian constant (A/g_∥) = 37.8×10⁻⁴ cm⁻¹, while for Dy(161) only four components could be seen, giving (A/g_∥) = 27.5×10⁻⁴ cm⁻¹. The observed linewidth for all lines was 25 Oe. The slope of the splitting between the two I = 0 resonances observed at 53 340 Oe and 67 590 Oe yields g_∥ = 19.3. The data indicates there is little departure from a linear Zeeman splitting at these high fields, and by extrapolation the antiferromagnetic zero field splitting is obtained. The zero field splitting agrees with the earlier spectroscopic results [J. C. Wright and H. W. Moos, Phys. Lett. 29 A, (1969).] only if an effective field of 1.3 kOe is added to the total dipolar field in the saturated state, indicating additional long‐range forces. The full version of this paper is being prepared for publication.