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 TN = 30.3K and TN = 3.85K 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 Hpz(T = 4K) ∼ 18T. The effect of strong magnetic fields is also studied in CeRhIn5, where an anomaly in the sample crystallographic c-axis of magnitude ∆c/c 2 ppm is found associated to a recently proposed electronic nematic state at Hen ∼ 30T applied 11 o off the c-axis. Here we show that while this anomaly is absent when the magnetic field is applied 18 o off the a-axis, strong magnetoelastic quantum oscillations attest to the high quality of the single crystal samples.Index Terms-magnetostriction, high magnetic fields, AFM domains, electronic nematic, UO2, CeRhIn5, FBG, quantum magnetoelastic oscillations arXiv:1811.03701v3 [cond-mat.str-el]

Piezomagnetic switching and complex phase equilibria in uranium dioxide

“…3a, the FBG magnetostriction measurements show that in this reversed field direction in the magnetic state, the response along the <111> direction is a linear contraction, displaying broken time-reversal symmetry, a characteristic of the piezomagnetic effect 13 . After reaching a certain temperaturedependent critical applied field strength 24 , the sample rapidly returns to the previous expansion response seen in the single direction applied field used in the first part of the experiment, then follows that path back to the same initial state at zero field. Looking at the integrated intensities of the diffracted peaks in Fig.…”

“…11 for more details and ref. 24 ). This behavior provides direct evidence that the "butterfly" hysteresis observed in the FBG experiment can therefore be related to piezomagnetic domain evolution revealed by X-rays.…”