Two-Dimensional Charge-Transport and Spin-Valve Effect in the Layered AntiferromagnetNd0.45Sr0.55MnO3

Abstract

Below the Nèel temperature ͑T N ͒ a layered antiferromagnetic (AF) Nd 0.45 Sr 0.55 MnO 3 crystal is metallic within the ferromagnetic (F) layers (ab plane), while insulating along the AF-coupling direction (c axis), showing an extremely large anisotropy in resistivity. The observed two dimensionality of charge dynamics is due to confinement of the spin-polarized carriers within the F sheets induced by the magnetic ordering as well as orbital ordering (perhaps of d x 2 2y 2 type). Large negative magnetoresistance is observed over a wide temperature region below T N , which arises from the dimensional crossover due to the field-induced spin canting in the AF state. [S0031-9007(99)

Peculiarities in low temperature properties of doped manganites A B MnO

“…Around x ∼ 0.5 new phenomena start to de-velop in doped manganites, such as charge ordering [33,34] [40]. Though some preparatory steps have been made to address these issues, e.g.…”

Tunneling magnetoresistance in nanogranular La1-xSrxMnO3 (x∼0.5)

“…Intrinsically, the electric conduction is metallic in FM planes of the A-type AFM structure and semiconducting in the perpendicular direction, i.e., along Mn chains with alternating +/-spins. 8 As the observed magnetoresistance in present ceramics is concerned, two sources of the extrinsic contribution should be considered: the first one is the field-dependent transfer of charge carriers between domains of different orientations of the conducting FM layers, and the second one is associated with the growth of FM regions in expense of AFM component, i.e., a kind of metamagnetic transition that is at the root of CMR effect appearing at phase boundaries of manganites.…”

“…6 In contrast to the exhaustive magnetoresistance studies focused on La 1-x Sr x MnO 3 manganites with "optimum strontium doping" (x∼0.3 leading to highest T C ), the present study deals with the field-dependent effects in "more doped" systems in a narrow composition region around x∼0.5; i.e., between the FM ground state of half-metallic character and A-type AFM ground state of anisotropic 2-dim metallic character. 7,8 In this respect three samples have been investigated -the highly dense bulks of compositions x=0.45 and 0.55, both prepared by a 2158-3226/2017/7(5)/055818/6 7, 055818-1 © Author(s) 2017…”

Magnetoelectric interfaces and spin transport

“…Important here is the fact that the ferromagnetic phase is half-metallic with electronic DOS only in the majority spin channel [68], whereas the antiferromagnetic phase has A-type magnetic order consisting of (001) planes of ferromagnetically ordered Mn moments that align antiparallel with neighbouring (001) planes. This magnetic structure leads to highly anisotropic 'two-dimensional' transport properties: metallic conductivity in the (001) plane and insulating behaviour along [001] [69].…”