By pulsed-laser deposition epitaxial thin films of Sr2FeMoO6 have been prepared on (100) SrTiO3 substrates. Already for a deposition temperature of 320• C epitaxial growth is achieved. Depending on deposition parameters the films show metallic or semiconducting behavior. At high (low) deposition temperature the Fe,Mo sublattice has a rock-salt (random) structure. The metallic samples have a large negative magnetoresistance which peaks at the Curie temperature. The magnetic moment was determined to 4 µB per formula unit (f.u.), in agreement with the expected value for an ideal ferrimagnetic arrangement. We found at 300 K an ordinary Hall coefficient of −6.01 × 10 −10 m 3 /As, corresponding to an electronlike charge-carrier density of 1.3 per Fe,Mo-pair. In the semiconducting films the magnetic moment is reduced to 1 µB/f.u. due to disorder in the Fe,Mo sublattice. In low fields an anomalous holelike contribution dominates the Hall voltage, which vanishes at low temperatures for the metallic films only.PACS numbers: 75.30. Vn, 73.50.Jt, The observation of colossal magnetoresistance in the half-metallic perovskite manganites has led to an intense research on ferromagnetic oxides.1 Recently, a large room temperature (RT) magnetoresistance was found in Sr 2 FeMoO 6 (SFMO) 2 , a material belonging to the class of double-perovskites (AA ′ BB ′ O 6 ).3 Depending on the metal ion radius the B and B ′ ions arrange in a random or ordered fashion. For the latter a layered or rock-salt structure is observed. The high Curie temperature and the high spin-polarization render these materials attractive as part of magnetic field sensors, e.g. in magnetic tunnel junctions. 4 The results reported lately on epitaxial thin film preparation on SrTiO 3 (STO) substrates are not consistent. Metallic as well as semiconducting behavior was found.5-7 Also the magnetic saturation moments were smaller than expected suggesting disorder in the rock-salt arrangement.8 Our goal was to find the preparation parameters for metallic, fully ordered films. We investigate in this letter in detail the differences between epitaxial metallic and semiconducting films with respect to their structural, magnetic and magnetotransport behavior, including Hall effect. We prepared a whole series of samples, but will discuss exhaustively two samples A and B which mark all the general differences.SFMO thin films were prepared by pulsed laser ablation in an oxygen partial pressure of 10 −1 − 10 −7 Torr or in argon atmosphere of 10 −1 Torr from a stoichiometric target on (100) STO substrates. During deposition the substrate temperature T D was constant with values covering the range from 300• C to 950 • C. Crystal structure investigations were performed using a twocircle and a four-circle X-ray diffractometer. The magnetic properties were determined with a SQUID magnetometer. With a Mireau interferometer we evaluated the film thicknesses to typically 100 nm. By standard photolithographic methods the samples were patterned to a 3 mm wide and 8 mm long bridge. The longi...
We report on detailed Hall-effect measurements of thin films of La 0.67 Ca 0.33 MnO 3 above and below the metal-insulator transition. In the metallic ferromagnetic regime, we find a temperature-independent holelike nominal charge-carrier density n h *ϭ1.3 per unit cell, consistent with a partly compensated Fermi surface. The mobility is only 92 mm 2 /V s at 4 K, and decreases with increasing temperature. Huge negative magnetoresistivity results from an increase in mobility. In low magnetic fields or at high temperatures, an anomalous electronlike contribution dominates the Hall voltage. For possible side jumps, we estimate an average jump length of the electron wave packet of 10 Ϫ13 m.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.