Magnetoelastics of High Field Phenomena in Antiferromagnets UO2 and CeRhIn5

Abstract

We use a recently developed optical fiber Bragg grating technique, in continuous and pulsed magnetic fields in excess of 90T, to study magnetoelastic correlations in magnetic materials at cryogenic temperatures. Both insulating UO2 and metallic CeRhIn5 present antiferromagnetic ground states, at $\mathrm{T}_{N}= 30.3\mathrm{K}$ and $\mathrm{T}_{N}= 3.85\mathrm{K}$ respectively. Strong coupling of the magnetism to the crystal lattice degrees of freedom in UO2 is found, revealing piezomagnetism as well as the dynamics of antiferromagnetic domain switching between spin arrangements connected by time reversal. The AFM domains become harder to switch as the temperature is reduced, reaching a record value $\mathrm{H}_{pz} (\mathrm{T} = 4\mathrm{K}) \sim 18\mathrm{T}$. The effect of strong magnetic fields is also studied in CeRhIn5, where an anomaly in the sample crystallographic c-axis of magnitude Δc/c ≃ 2 ppm is found associated to a recently proposed electronic nematic state at $\mathrm{H}_{en} \sim 30\mathrm{T}$ applied 11° off the c-axis. Here we show that while this anomaly is absent when the magnetic field is applied 18° off the a-axis, strong magnetoelastic quantum oscillations attest to the high quality of the single crystal samples.