Magnetoelectrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi2B2C

Abstract

We report our observation of the behavior of the radio frequency (rf) and microwave response of DyNi2B2C over a wide range of temperature (T) and magnetic field (H) in the antiferromagnetic (AFM) and superconducting (SC) states. At microwave frequencies of 10 GHz, the T dependence of the surface impedance Zs=Rs+iXs was measured which yields the T dependence of the complex conductivity σ1−iσ2 in the SC and AFM states. At radio frequencies (4 MHz), the H and T dependence of the penetration depth λ(T,H) were measured. The establishment of antiferromagnetic order at TN=10.3K results in a marked decrease in the scattering of charge carriers, leading to sharp decreases in Rs and Xs. However, Rs and Xs differ from each other in the AFM state. We show that the results are consistent with relaxation processes whence the scattering rate becomes comparable to the microwave frequency. The rf measurements yield a rich dependence of the scattering on the magnetic field near and below TN. Anomalous decrease of scattering at moderate applied fields is observed at temperatures near and above TN, and arises due to a crossover from a negative magnetoresistance state, possibly associated with a loss of spin disorder scattering at low fields, to a positive magnetoresistance state associated with the metallic nature. The normal state magnetoresistance is positive at all temperatures for μ0H>2T and at all fields for T>15K. Several characteristic field scales associated with metamagnetic transitions [HM1(T),HM2(T)], the onset of spin disorder HD(T) and the upper critical field Hc2(T) are observed in the rf measurements.

Source-reported materials — not catalogue approval

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