Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films

Abstract

The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system. Despite extensive efforts for several decades, no material system has been clearly identified to exhibit all three transport regimes characteristic of the two-channel Kondo effect in the same sample, leaving the interpretation of the experimental results a subject of debate. Here we present a transport study suggestive of a robust orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films, as evidenced by a magnetic field-independent resistivity upturn with a clear transition from logarithmic- to square-root temperature dependence and deviation from it in three distinct temperature regimes. Our results also provide an experimental indication of the presence of two-channel Kondo physics in a ferromagnet, pointing to considerable robustness of the orbital two-channel Kondo effect even in the presence of spin polarization of the conduction electrons.

Anomalous Hall effect and spin-orbit torques in MnGa/IrMn films: Modification from strong spin Hall effect of the antiferromagnet

“…should be manifested as a decreased magnitude and an enhanced effective breakdown temperature of the 2CK effect as a result of the enhanced decoupling of TLS from one spin channel [34]. Therefore, the orbital 2CK effect in the FM will be suppressed when contacting with a strong SOC metal, since the pure spin current generated by SHE will diffuse into the FM layer and enhance the channel asymmetry.…”

“…The orbital two-channel Kondo (2CK) effect displaying exotic non-Fermi liquid (NFL) behavior arises in the intricate scenario of two conduction electrons compensating a pseudo-spin 1/2 impurity of two-level system (TLS) [34]. The orbital 3 2CK effect from TLSs is manifested in electrical transport by a unique temperature (T) dependence in resistivity with three distinct T regimes: a low-T upturn characterized by  xx~l nT for T beyond Kondo temperature T K , followed by NFL behavior  xx~ T 1/2 for T D <T<T K and deviation from T 1/2 dependence upon further cooling [34,35].…”

Topological Majorana Two-Channel Kondo Effect

“…Realizing the 2CK effect without fine-tuning the channel symmetry has long been an unrealized dream. Recently, three experiments have provided compelling evidences for spin, charge, and orbital 2CK effects in highly fine-tuned double QDs [51], ν = 1 quantum Hall liquid [52], and ferromagnetic L1 0 -MnAl [53], respectively. In this Letter, we demonstrate the realization of a topologically protected, channel-symmetric, 2CK effect without fine-tuning in the Majorana transistor.…”

Enhanced spin-orbit torques in MnAl/Ta films with improving chemical ordering

“…23,24 On the other hand, L1 0 -MnAl films with high bulk PMA are also ideal for a systematic examination of SOT, in which the related magnetic and transport behaviors can be controllably varied with thermally tuned chemical ordering. 21,22 In this work, we report the SOT A 3-nm-thick L1 0 -MnAl single-crystalline film was grown on a semi-insulating GaAs (001) substrate by molecular-beam epitaxy at substrate temperature T S =250 º C, in which the Mn/Al atoms ratio is 1. 25 Then, 5-nm-thick Ta film was deposited on it by dc magnetron sputtering.…”

“…6,19 On the contrary, the PMA originating from bulk rather than interface seems to be stable and also can be improved by thermal treatment. [20][21][22] Recently, we have systematically investigated the SOT based on L1 0 -MnGa films with bulk PMA, which seems to be an ideal FM for investigating SOT. 23,24 On the other hand, L1 0 -MnAl films with high bulk PMA are also ideal for a systematic examination of SOT, in which the related magnetic and transport behaviors can be controllably varied with thermally tuned chemical ordering.…”