Evidence for spin mixing in holmium thin film and crystal samples

Abstract

In a number of recent experiments, holmium has been shown to promote spin triplet pairing when in proximity to a spin singlet superconductor. The condition for the support of spin triplet pairing is that the ferromagnet should have an inhomogeneous magnetic state at the interface with the superconductor. Here we use Andreev reflection spectroscopy to study the properties of single ferromagnet/superconductor interfaces formed of holmium and niobium, as a function of the contact resistance of the junction between them. We find that both single crystal and c-axis oriented thin film holmium show unusual behavior for low junction contact resistance, characteristic of spin mixing type properties, which are thought necessary to underpin spin triplet formation. We also explore whether this signature is observed when the junction is formed of Ni 19 Pd 81 and niobium.

Supercurrent enhancement in Bloch domain walls

“…This means that it is practically impossible to probe the effect that DWs have on the supercurrents that pass through them. As an alternative, intrinsically DW-like ferromagnets such as Ho can be used 36 and indeed our group 20 37 (see also Ref. 38 ) and Sosnin et al 19 have demonstrated results consistent with a triplet proximity effect in Ho-based junctions.…”

Theory of the spin-galvanic effect and the anomalous phase shiftφ0in superconductors and Josephson junctions with intrinsic spin-orbit coupling

“…The spatial oscillatory behavior of the superconducting condensate induced in the ferromagnet leads to interesting effects as oscillations of the density-of-state in F/S [3][4][5] and F/S/F [6] structures, oscillations of the Josephson current in S/F/S Josephson junction [7][8][9][10], and oscillations of the critical temperature [1]. Moreover, in the case of multi-domain ferromagnets or artificial multilayer structures with inhomogeneous magnetization, the singlet Cooper pairs from a superconductor can be transform into long-range triplet pairs that may explain the long-range Josephson coupling observed in S/F/S structures [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Triplet correlations also leads to a dependence of the critical current on the magnetic configuration of diverse S/F structures [26][27][28][29][30][31][32][33].…”

Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

“…It has been experimentally [24][25][26] and theoretically [27][28][29][30] proved that Ho can convert the singlet state into spin-aligned triplet state. This conversion can open a proximity channel for singlet Cooper pairs into linear ferromagnets, resulting in T c reduction.…”