Influence of a 36.8° grain boundary on the magnetoresistance of La0.8Sr0.2MnO3−δ single crystal films

Abstract

Epitaxial ferromagnetic manganite films have been sputtered on bicrystal substrates. Their magnetoresistance was measured as a function of magnetic field and temperature. The grain boundary magnetoresistance at low temperature is separated from the intrinsic magnetoresistance near the Curie temperature. The grain boundary magnetoresistance peaks at about 100 Oe and saturates at about 2 kOe. For a La0.8Sr0.2MnO3 film with a grain boundary angle θ=36.8° a field independent component r0=4.1×10−6 Ω cm2 was separated from a field-dependent component which has its maximum rH=2.3×10−6 Ω cm2 for H of order the coercive field.

Magnetotransport properties of a single grain boundary in a bulk La–Ca–Mn–O material

“…Therefore the single boundaries in bulk materials and thin films do not behave in a similar manner. This is confirmed by examining the hysteresis of the R(H) curves: in thin films single boundaries, the hysteresis only concerns the LFMR, 15,23 while in our case a very small hysteresis, 20 mT, can be observed throughout the whole magnetic field range and temperature investigated.…”

“…11,15,18 In thin films single boundaries, the H* field roughly corresponds to the coercive field of the adjacent grains, 18 whereas in ceramics, H* is linked to the saturation field, 11 as it is the case for the single boundaries in bulk materials presented in this article. Therefore the single boundaries in bulk materials and thin films do not behave in a similar manner.…”

“…[10][11][12] Most of the systematic investigations devoted to individual grain boundaries have thus been carried out in thin films. By growing epitaxial thin films on bicrystal substrates, [13][14][15][16][17][18] well-controlled grain boundaries can be obtained. For example, Evetts et al 18 have studied films patterned in such a way that only the contribution of the grain boundary to the resistance is measured.…”

Stoner–Wohlfarth model applied to bicrystal magnetoresistance hysteresis

“…In order to understand and exploit this effect several studies have used bicrystal grain boundary junctions [6,7,8]. Since bicrystals are samples with well defined crystal orientations with respect to an interface, they are in a way ideal systems for studies of the behaviour of magnetic tunnel junctions.…”

Thin–film trilayer manganate junctions

“…The role of grain boundary in providing additional contributions to low-field magnetoresistance has long been suspected (Ju et al, 1995;Gupta et al, 1996;Hwang et al, 1996). Direct experimental observation of grain-boundary-originated magnetoresistance has recently been made (Mathur et al, 1997;Steenbeck et al, 1997) which shows a 30% magnetoresistance in a field of less than 500 Oe.…”