Crossover between weak anti-localization and weak localization by Co doping and annealing in gapless PbPdO2 and spin gapless Co-doped PbPdO2

Abstract

The magnetotransport properties of Pb(Pd,Co)O2 and PbPdO2 thin films were investigated. In magnetoconductance curves, we observed a crossover between weak anti-localization (WAL) and weak localization (WL) depending on the annealing and Co doping in PbPdO2 thin films. For the Pb(Pd,Co)O2 case showing WAL signals, the ex-situ annealing weakens the Pd-O hybridization by stabilizing Co3+ states and generating Pd1+ states, instead of Pd2+, so that the spin-orbit coupling (SOC) strength is significantly reduced. It causes the dominant magnetotransport mechanism change from WAL to WL. This annealing effect is compared with the PbPdO2 case, which possesses WL signals. The annealing process stabilizes the oxygen states and enhances the Pd-O hybridization, and consequently the SOC strength is enhanced. Our experimental results are well explained by the Hikami-Larkin-Nagaoka theory in terms of two important physical parameters; SOC strength-related α and inelastic scattering length lϕ.

Ab-initio investigation of electronic and magnetic properties of the 18-valence-electron fully-compensated ferrimagnetic (CrV)XZ Heusler compounds: A prototype for spin-filter materials

“…All these compounds have also 18 valence electrons per f.u. being fully-compensated ferrimagnets, but show even more interesting behavior in electronic states around Fermi energy like the ferrimagnetic gapless-semiconducting [27] or the spin-gapless-semiconducting behavior [24,[27][28][29]. In the former there is a zero energy gap in both spin directions but the bands are different for the two spin-directions, while in the latter there is a zero gap for the one spin-direction and a finite gap for the other spin-direction.…”

Effects of V and Gd doping on novel positive colossal electroresistance and quantum transport in PbPdO2 thin films with (002) preferred orientation

“…Therefore, a series of subsequent related studies mainly focused on doping different magnetic or non-magnetic atoms into PbPdO 2 , and subsequently exploring electrical, magnetic, and thermal properties after ion doping. 7–13 In 2010, Lee et al investigated the resistivity behavior of PbPdO 2 and PbPd 0.9 Co 0.1 O 2 , observing a transition from high-temperature metallic behavior to low-temperature insulating behavior at 100 K for PbPdO 2 , while the transition temperature ( T MI ) increased to 150 K for PbPd 0.9 Co 0.1 O 2 . 7 They further examined the magnetoresistance curve as a function of temperature at low temperatures and attributed the magnetic and magnetic transport properties of these materials to their strong spin–orbit coupling (SOC), which is characteristic of zero-band gap semiconductors.…”

Strain Engineered Band Gaps and Electronic Properties in PbPdO2 and PbPd0.75Co0.25O2 Slabs

“…Based on the bound magnetic polaron (BMP) theory, the potential mechanism behind the observed ferromagnetic, paramagnetic, and antiferromagnetic properties coexisting in Co–doped PbPdO 2 film were suggested [ 8 ]. It was suggested that Pd–O hybridization in Co–doped PbPdO 2 thin films were responsible for the transition from weak localization and weak anti-localization [ 9 ]. Simultaneously, many studies on valence states and band structures have been carried out to understand the mechanism on the observed physical behaviors.…”