Coexistence of ferromagnetism and superconductivity inErRh4B4single crystals probed by dynamic magnetic susceptibility

Abstract

High-resolution measurements of the dynamic magnetic susceptibility are reported for the ferromagnetic, reentrant superconductor ErRh 4 B 4 . A detailed investigation of the coexisting regime reveals unusual temperature-asymmetry on warming and cooling and magnetically anisotropic behavior. The superconducting phase appears via a series of discontinuous steps upon warming from the ferromagnetic normal phase, whereas the ferromagnetic phase develops via a more gradual transition upon cooling from the superconducting phase. A model based on local field inhomogeneity is proposed to explain these observations.

Superconductivity and magnetism on flux-grown single crystals of NiBi3

“…Successive transitions between superconductivity and other ordered states are observed in Chevrel phase and borocarbide compounds. [11][12][13][14][15][16][17][18] Superconducting properties have been shown to be enhanced by an external field. [19][20][21][22][23] In heavy fermions and in hybrid proximity ferromagnetic-superconducting structures, magnetism can induce unconventional p-wave or other forms of complex superconductivity.…”

Evolution of the Local Superconducting Density of States inErRh4B4Close to the Ferromagnetic Transition

“…These areas show the spectroscopic features discussed in the following. These features are much sharper than those found on macroscopic measurements [1,2,3,13,14,15,16,17,18], which should, even in high quality samples, give an averaged behavior. At the lowest temperatures, T=0.3 K, only the superconducting features due to the Pb tip are observed in the tunneling conductance curves, and N ErRh4B4 (E) is flat and featureless.…”

“…This is a reentrant superconductor in which, with decreasing temperature, first a superconducting transition occurs, at T c1 ≈ 8 K, and then at T c2 ≈ 0.7 K, where local Er moments order ferromagnetically, the material becomes normal again. Until now this material was only probed with macroscopic probes, such as thermal studies, resistivity and susceptibility, neutron scattering or tunneling spectroscopy using thing films [1,2,3,13,14,15,16,17,18]. The superconducting properties far from the magnetic transition remain unknown to a large extent.…”

“…When heating, the transition to the full superconducting state occurs T c2↑ , which is considerably above (around 100 mK) the transition temperature found when cooling, T c2↓ . There are no pronounced effects associated with the velocity of the temperature ramps, so it seems that superconductivity truly hinders the outcome of ferromagnetism and viceversa [3,17,18]. Remarkably, neutron scattering experiments by Sinha et al [13] have shown that in the superconducting phase, when cooling, a new magnetically modulated state appears around 1 K, and disappears below T c2↓ .…”

“…This peculiar magnetic state is supposed to be induced by superconductivity [3], as proposed by Anderson and Suhl [3,19]. More recently, it has been shown that the modulated state most likely coexists within superconducting domains forming close to ferromagnetism [17,18]. There are many important open questions raised by these and other studies.…”