Colossal negative magnetoresistance from hopping in insulating ferromagnetic semiconductors

Abstract

Ferromagnetic semiconductor Ga1–x Mn x As1–y P y thin films go through a metal–insulator transition at low temperature where electrical conduction becomes driven by hopping of charge carriers. In this regime, we report a colossal negative magnetoresistance (CNMR) coexisting with a saturated magnetic moment, unlike in the traditional magnetic semiconductor Ga1– x Mn x As. By analyzing the temperature dependence of the resistivity at fixed magnetic field, we demonstrate that the CNMR can be consistently described by the field dependence of the localization length, which relates to a field dependent mobility edge. This dependence is likely due to the random environment of Mn atoms in Ga1–x Mn x As1–y P y which causes a random spatial distribution of the mobility that is suppressed by an increasing magnetic field.

Anomalous metallic conductivity and short-range ferromagnetic correlation in high-pressure synthesized pyrochlore

“…2(a). No visible magnetic phase transition can be observed down to 2 K. Between 100 and 300 K, the susceptibility is nearly temperature-independent [32,33]. On the other hand, we found that the paramagnetic susceptibility in the temperature range of 300-400 K can be well fitted with the Curie-Weiss law as shown in fig.…”

Colossal negative magnetoresistance in spin glass Na(Zn,Mn)Sb

“…Large AHE has also been found in SGlike Ge 1-x-y Sn x Mn y Te [30] . The AHE indicates strong spin-orbit coupling and spin polarization [31] . The hole concentrations of single crystal Na 1.09 (Zn 0.88 Mn 0.12 )Sb is 3.0 × 10 19 cm −3 at 100 K, which is over three times larger than that of parent phase.…”

Anomalous bond lengthening in compressed magnetic doped semiconductor Ba(Zn0.95Mn0.05)2As2

“…Thus, it is essential to study structural parameters and the possible phase transition under external pressures. Aforementioned (Ba,K)(Zn,Mn) 2 As 2 belongs to a new type of DMS with independent carrier and spin doping [24,25] , which is a key feature distinguished from (Ga,Mn)As [26] . Its parent material BaZn 2 As 2 has two phases.…”