Large low-field magnetoresistance in La0.7Ca0.3MnO3 induced by artificial grain boundaries

Mathur, N. D.; Burnell, Gavin; Isaac, Shabtai; Jackson, Trevor; Teo, B.-S.; MacManus‐Driscoll, Judith L.; Cohen, L. F.; Evetts, J.E.; Blamire, M. G.

doi:10.1038/387266a0

Cited by 446 publications

(249 citation statements)

References 23 publications

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“…4 Therefore, LFMR should be especially important in granular systems 4 -7 and artificially generated interfaces. 8 In fact, LFMR responses near 30% have been found in granular systems at low temperatures, but on raising temperature a substantial reduction is observed well below T C . This reduction is mainly due to the depolarization of the conduction charge carriers because of the scattering generated at magnetically disordered interfaces in GB.…”

Section: Introductionmentioning

confidence: 99%

Enhanced low field magnetoresistive response in (La2/3Sr1/3MnO3)x/(CeO2)1−x composite thick films prepared by screen printing

València

Castaño

Fontcuberta

et al. 2003

Journal of Applied Physics

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The magnetoresistance and magnetization of (La2/3Sr1/3MnO3)x(LSMO)/(CeO2)1−x (0.64⩽x⩽1) composite thick films have been studied as a function of the manganite concentration. It is found that for high LSMO content, when the applied magnetic field is perpendicular to the film plane, the attainable low field magnetoresistance (LFMR) response is drastically reduced due to demagnetizing field effects. These effects are suppressed when the concentration of CeO2 is increased, thus an enhancement of the LFMR is observed. These results can be very important for developing magnetic sensors working in the low magnetic field regime when magnetic field needs to be applied perpendicular to the film plane.

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Section: Introductionmentioning

confidence: 99%

Enhanced low field magnetoresistive response in (La2/3Sr1/3MnO3)x/(CeO2)1−x composite thick films prepared by screen printing

València

Castaño

Fontcuberta

et al. 2003

Journal of Applied Physics

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“…Examples of the latter are the giant magnetoresistance of multilayers [4] and granular metals [5,6] or the behavior of spin-dependent tunnel junctions [7], where resistivity is greatest at the coercive or switching field and decreases as the sample reaches technical saturation. Recent experiments on epitaxial manganite films with a single grain boundary have allowed the high-field, colossal magnetoresistance to be separated from the low-field effect due to heterogeneous magnetization distribution in adjacent grains [8,9]. A characteristic but unexplained feature of the low-field magnetoresistance in manganite ceramics [10], polycrystalline films [11,12], and tunnel junctions [13,14] is its rapid decay with increasing temperature.…”

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confidence: 99%

Magnetoresistance of Chromium Dioxide Powder Compacts

et al. 1998

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Cold-pressed powders of the half-metallic ferromagnet CrO 2 are dielectric granular metals. Hysteretic magnetoresistance with maxima at the coercive field arises from interparticle contacts. Dilution with insulating antiferromagnetic Cr 2 O 3 powder reduces the conductivity by 3 orders of magnitude, but enhances the magnetoresistance ratio which reaches 50% at 5K. The negative magnetoresistance is due to tunneling between contiguous ferromagnetic particles along a critical path with a spin-dependent Coulomb gap. [S0031-9007(98)05996-1] PACS numbers: 72.15. Gd, 73.40.Gk, 75.50.Cc, 81.20.Ev Negative magnetoresistance has been widely investigated in ferromagnetic metals and heterostructures. Effects intrinsic to a material are distinguished from extrinsic effects which depend on the direction of magnetization in adjacent ferromagnetic regions. Examples of the former include the anisotropic magnetoresistance of permalloy [1] or the colossal magnetoresistance of nonstoichiometric EuO [2] and mixed-valence manganites [3]. Examples of the latter are the giant magnetoresistance of multilayers [4] and granular metals [5,6] or the behavior of spin-dependent tunnel junctions [7], where resistivity is greatest at the coercive or switching field and decreases as the sample reaches technical saturation. Recent experiments on epitaxial manganite films with a single grain boundary have allowed the high-field, colossal magnetoresistance to be separated from the low-field effect due to heterogeneous magnetization distribution in adjacent grains [8,9]. A characteristic but unexplained feature of the low-field magnetoresistance in manganite ceramics [10], polycrystalline films [11,12], and tunnel junctions [13,14] is its rapid decay with increasing temperature.Here we report a new type of extrinsic magnetoresistance. It is studied in pressed powders of CrO 2 , where it arises from contacts between particles. Chromium dioxide is an ideal material for spin-polarized electron tunneling, as it is a half-metallic ferromagnet where complete spin polarization of the conduction electrons is maintained up to the surface [15]. There are two 3d electrons in spinsplit t 2g subbands, one localized and the other in a halffilled band [16]. The two electrons are strongly coupled by the on-site exchange interaction J H ഠ 1 eV. The intrinsic metallic nature of the oxide is illustrated by the resistivity of an oriented film grown on TiO 2 , shown in Fig. 1(a). It follows Matthiessen's rule with a residual resistivity of 0.1 mV m ͑10 mV cm͒ and a room-temperature value about 30 times greater. The slope dr͞dT remains positive above the Curie temperature ͑T C 396 K͒ [17]. The films exhibit only a small linear intrinsic magnetoresistance effect, ͑1͞m 0 r͒dr͞dH ϳ1%͞T at room temperature.Our samples were made from a commercial CrO 2 powder used for magnetic recording. The powder is composed of acicular single-domain particles with an average length of 300 nm and an aspect ratio of about 8:1. Coercivity is 59 mT (590 G) at room temperature, rising up to ...

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“…Other approaches are to produce polycrystalline films 3 , bulk materials 4 , ramp-edge junctions 5 , or thin films which are under compressive strain 6 . As is well known from the high-T C superconductors, a further access is to deposit thin manganite films on bicrystal substrates to realize a single artificial grain boundary (GB) 7,8 . In order to understand the mechanism of the large lowfield MR, we have carefully studied the resistivity of thin manganite films with and without an artificial GB, induced by a bicrystal substrate, as a function of temperature, magnetic field and current.…”

Section: Introductionmentioning

confidence: 99%

Current dependence of grain boundary magnetoresistance in La0.67Ca0.33MnO3 films

Westerburg

Martin

Friedrich

et al. 1999

Journal of Applied Physics

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We prepared epitaxial ferromagnetic manganite films on 45 • bicrystal substrates by pulsed laser ablation. Their low-and high-field magnetoresistance (MR) was measured as a function of magnetic field, temperature and current. At low temperatures hysteretic changes in resistivity up to 70 % due to switching of magnetic domains at the coercitive field are observed. The strongly non-ohmic behavior of the current-voltage (I-V ) leads to a complete suppression of the MR effect at high bias currents with the identical current dependence at low and high magnetic fields. We discuss the data in view of tunneling and mesoscale magnetic transport models and propose an explicit dependence of the spin polarization on the applied current in the grain boundary region.

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Large low-field magnetoresistance in La0.7Ca0.3MnO3 induced by artificial grain boundaries

Cited by 446 publications

References 23 publications

Enhanced low field magnetoresistive response in (La2/3Sr1/3MnO3)x/(CeO2)1−x composite thick films prepared by screen printing

Enhanced low field magnetoresistive response in (La2/3Sr1/3MnO3)x/(CeO2)1−x composite thick films prepared by screen printing

Magnetoresistance of Chromium Dioxide Powder Compacts

Current dependence of grain boundary magnetoresistance in La0.67Ca0.33MnO3 films

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