Low‐Field Magnetoresistance in La_0.67Sr_0.33MnO₃:ZnO Composite Film

Abstract

A nanocomposite fi lm of La 0.67 Sr 0.33 MnO 3 (LSMO):ZnO is synthesized by depositing LSMO solution on a vertical array of ZnO nanorods grown on (0001) Al 2 O 3 substrate. The magnetic behavior of the composite fi lm differs from that of a pure LSMO fi lm, possibly due to smaller grain size in the composite, small amount of Zn doping, or the presence of nonmagnetic ZnO phase near the LSMO grain boundaries. Magnetotransport measurements show that the low-fi eld magnetoresistance (LFMR) of the nanocomposite fi lm is signifi cantly enhanced as compared to that observed for pure LSMO fi lm. The highest value of the LFMR of the nanocomposite fi lm at 10 K is -23.9% with a magnetic fi eld of 0.5 T applied parallel to the current.

Enhancement of Low-field Magnetoresistance in Self-Assembled Epitaxial La0.67Ca0.33MnO3:NiO and La0.67Ca0.33MnO3:Co3O4 Composite Films via Polymer-Assisted Deposition

“…Moreover, the peak resistivity of these two composite films (0.59 Ω•cm for LCMO:10%-NiO and 1.07 Ω•cm for LCMO:10%-Co 3 O 4 at zero magnetic field) are much higher than that of the single phase LCMO film (0.0061 Ω•cm at zero magnetic field). These two observations can be attributed to the presence of a large number of the grain boundaries, increased disorder, as well as insulating phase-induced barriers to the electrical transport14313233. The introduced insulating phase at the grain boundary has been known to obstruct the magnetic spin alignment near the grain boundary region.…”

“…Also, the resistivity increases for the LCMO:30%-Co 3 O 4 composite film in comparison to that of the LCMO:10%-Co 3 O 4 composite film. This is because the metal-insulator transition was suppressed by the expansion of in-plane lattice parameter in LCMO1422.…”

“…For example, LCMO:ZrO 2 (LCMO: La 0.67 Ca 0.33 MnO 3 ) composite films produced by the sol-gel method achieved a MR value of −31% at 77 K under 0.1 T21. Also, −25% of MR at 93 K under 1.15 T was observed in LCMO:15% V 2 O 5 composite fabricated by a two-step solid-state reaction22 and a pronounced LFMR of −23.9% at 10 K in a field of 0.5 T was achieved in LSMO:ZnO (LSMO: La 0.67 Sr 0.33 MnO 3 ) composite film14. Finally, a tunable and enhanced LFMR of −30% at 154 K under 0.1 T was observed in a LSMO:ZnO nanocomposite film grown by pulsed-laser deposition (PLD).…”

“…Many reported works have suggested that the regions of structural disorder generated during the film deposition, grain boundaries in short, are the dominant factors in achieving the enhanced low-field magnetoresistance (LFMR). Also introducing a second phase, especially the insulating phase, into La 1−x A x MnO 3 films has been considered an effective approach for engineering the grain boundaries8910111213141516171819202122. For example, LCMO:ZrO 2 (LCMO: La 0.67 Ca 0.33 MnO 3 ) composite films produced by the sol-gel method achieved a MR value of −31% at 77 K under 0.1 T21.…”

Exchange Bias Effect and Magnetic Properties in ${\hbox{La}}_{0.7}{\hbox{Sr}}_{0.3}{\hbox{MnO}}_{3}\hbox{-}{\hbox{NiO}}$ Nanocomposite Films

“…What is more, in the past few years the effect of grain boundaries in LSMO has been studied intensively [5]- [8]. It was found that the secondary phase at the boundary not only can lead to a large low field magnetoresistance (LFMR) but also a large change in the intrinsic magnetic properties, i.e., the ferromagnetic transition temperature ( ) and the coercive field ( ) at low temperature [9], [10]. Although the doping effects of the nano-impurities on the electrical and magnetic properties in the bulk composite samples have been investigated by several groups [11]- [13], the magnetic interaction at the boundaries Manuscript (EB effect) and magnetotransport behaviors of the nanocomposite thin films has rarely been studied [14].…”