Transport properties in manganite thin films

Abstract

The resistivity of thin $La_{0.7}A_{0.3}MnO_{3}$ films ($A=Ca, Sr$) is investigated in a wide temperature range. The comparison of the resistivities is made among films grown by different techniques and on several substrates allowing to analyze samples with different amounts of disorder. In the low-temperature nearly half-metallic ferromagnetic state the prominent contribution to the resistivity scales as $T^{\alpha}$ with $\alpha \simeq 2.5$ for intermediate strengths of disorder supporting the theoretical proposal of single magnon scattering in presence of minority spin states localized by the disorder. For large values of disorder the low-temperature behavior of the resistivity is well described by the law $T^{3}$ characteristic of anomalous single magnon scattering processes, while in the regime of low disorder the $\alpha$ exponent tends to a value near 2. In the high temperature insulating paramagnetic phase the resistivity shows the activated behavior characteristic of polaronic carriers. Finally in the whole range of temperatures the experimental data are found to be consistent with a phase separation scenario also in films doped with strontium ($A=Sr$).Comment: 5 figure

Electrical Transport and Magnetoresistance of La0.67Ca0.33MnO3: Agx(x = 0, 0.1, 0.2, 0.3, 0.4) Composites

“…8. In previous studies on composite perovskites [11,[27][28][29][30][31][32][33][34], the increase in MR values at low temperatures has been attributed to grain boundary effects introduced by the dopant. Although, the mechanism of the grain boundary induced MR is not yet clear, some models have been proposed.…”

“…As mentioned above, ρ 0 represents the resistance contribution due to the grain boundary effect. In many studies, it has been concluded that the value of ρ 0 can be considered a measure of the effective disorder [31]. In this case the increase of ρ 0 with Ag can be interpreted as a higher value of Ag and results in poor crystallinity with a disordered grain boundary structure.…”

Tailoring magnetic anisotropy in epitaxial half metallic La0.7Sr0.3MnO3 thin films

“…In addition, it is worth mentioning that the measurements of temperature dependent resistivity (q(T)), performed in a 4-square contact geometry for the different LSMO films investigated typically show very low residual resistivity (q(10 K) % 0.1 Â 10 -6 Xm), confirming their high crystal quality. 28 The morphology of the samples was investigated by means of scanning probe microscopy, in particular by AFM and STM. The average roughness (RMS) of the samples was found in the range of few unit cells (u.c.)…”

Thickness dependent transport properties of compressively strained La0.88Sr0.12MnO3 ultrathin films

“…Extensive studies have been carried out on thin films of La 1−x Sr x MnO 3 . [39][40][41][42][43][44][45][46][47][48][49][50][51][52] The effects of strainfilm-thickness-induced modifications in various physical properties, such as magnetotransport and magnetic properties, [44][45][46][47][48][49][50][51][52][53][54][55][56][57] magnetic anisotropy, 39,40 optical properties, 40,50 and conduction noise, 38 have been investigated. However, nearly all of the studies related to the effect of strain have focused on La 1−x Sr x MnO 3 with a doping level of x ϳ 0.3 in which the one electron ͑e g ͒ bandwidth is large.…”