Room-temperature magnetoresistance in an oxide material with an ordered double-perovskite structure

Abstract

Nature © Macmillan Publishers Ltd 19988 the fact that we have a quantized Hall resistance deep inside the insulator. Indeed, j 2 xx j xy 2 e 2 2h 2 e 2 2 h 12e 2 =hr xy r 2 xx r 2 xy simply from matrix inversion. As noted by Shahar et al. 10 , the semicircle relation follows directly as long as r xy h=e 2 . In addition, it is completely independent of the value of r xx . We emphasize that this relation holds for our entire range of T. Ando 21 ®rst calculated numerically the dependence of j xx on j xy and found a similar relation to the semicircle function. In the selfconsistent Born approximation and scaling theories, a behaviour of this kind is also expected 22 . A recent numerical study by R. N. Bhatt and S. Subramanian (personal communication), with symmetric and non-symmetric random potentials in a lowest-Landau-level model, con®rmed this result. For higher Landau levels, Wei et al. 23 and others 10 showed similar dependences. This is, however, the ®rst clear demonstration of this relation for n # 1 and j xx and j xy both smaller than e 2 /2h.The experiments presented covered a certain range of parameters, in particular in temperature and in disorder. Different behaviours occurring at even lower temperatures or higher mobilities are therefore possible and would be interesting to investigate in future. The existence of these insulators, however, can serve as guidelines for a complete understanding of two-dimensional systems in strong magnetic ®elds. M

Unusual electron-doping effects inSr2−xLaxFeMoO6Saitoh1, Nakatake2, Nakajima3 et al. 2005Phys. Rev. B192130View full textAdd to dashboardCite

“…A comparison with the band-structure calculations clarifies that the double-peak structures A and B near E F correspond to the (Fe+Mo) t 2g↓ and Fe e g↑ bands, respectively. 1,6,7,8,9,11,12 Also, C and D mostly originate from the Fe t 2g↑ bands with a contribution from the O 2p intensity. E is predominantly due to the O 2p non-bonding states.…”

Spin reorientation and disordered rare earth magnetism in Ho2FeCoO6

“…The research on double perovskites extends over bulk as well as thin films in order to realize usable multiferroic device elements [1,2,3,4]. In addition to multiferroicity [2], observation of metamagnetic steps in magnetization [5], exchange bias [6], magnetoresistance and magnetocapacitance [7] make these compounds interesting.…”

Direct Observation of Cationic Ordering in Double Perovskite Sr2FeReO6 Crystals

“…Moreover, these double perovskites have become one of a group of promising magnetic materials for spin electronics because of their high T c , the value of which is much higher than 300 K, and their tunneling-type magnetoresistancẽ Kobayashi et al, 1998;Fang et al, 2001!. The magnetic structure of A 2 BB ' O 6 is known to originate from the ordered arrangement of parallel Fe 3ϩ~3 d 5 , S ϭ 5/2!…”