Pulsed-laser-deposited epitaxial Sr2FeMoO6−y thin films: Positive and negative magnetoresistance regimes

Asano, Hidefumi; Ogale, S. B.; Garrison, J.; Orozco, Antonio; Li, Y. H.; Li, E.; Smolyaninova, Vera N.; Galley, Chad R.; Downes, M.; Rajeswari, M.; Ramesh, R.; Venkatesan, T.

doi:10.1063/1.123224

Cited by 92 publications

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References 22 publications

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“…The room temperature resistivity value of 3 mΩcm is comparable with other reported results 6 , but down to 4 K the resistivity increases almost an order of magnitude. Depending on preparation the sign of the temperature coefficient and the sign of the MR changes 7 . We observed in our semiconducting films a negative MR of -3.5 % at a temperature of 4 K and a magnetic field of 8 T, similar to the result of Asano et al 7 .…”

Section: Resultsmentioning

confidence: 99%

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Hall effect of epitaxial double-perovskite Sr2FeMoO6 thin films

Westerburg

Martin

Jakob

2000

Journal of Applied Physics

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We prepared high epitaxial thin films of the compound Sr2FeMoO6 with narrow rocking curves by pulsed laser deposition. The diagonal and nondiagonal elements of the resistivity tensor were investigated at temperatures from 4 K up to room temperature in magnetic fields up to 8 T. An electronlike ordinary Hall effect and a holelike anomalous Hall contribution are observed. Both coefficients have reversed sign compared to the colossal magnetoresistive manganites. We found at 300 K an ordinary Hall coefficent of −1.87 × 10 −10 m 3 /As, corresponding to a nominal charge carrier density of four electrons per formula unit. At low temperature only a small negative magnetoresistance is observed which vanishes at higher temperatures. The temperature coefficient of the resistivity is negative over the whole temperature range. A Kondo like behavior is observed below 30 K while above 100 K variable range hopping like transport occurs.

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Section: Resultsmentioning

confidence: 99%

“…Depending on preparation the sign of the temperature coefficient and the sign of the MR changes 7 . We observed in our semiconducting films a negative MR of -3.5 % at a temperature of 4 K and a magnetic field of 8 T, similar to the result of Asano et al 7 . At higher temperatures the MR vanishes.…”

Section: Resultsmentioning

confidence: 99%

Hall effect of epitaxial double-perovskite Sr2FeMoO6 thin films

Westerburg

Martin

Jakob

2000

Journal of Applied Physics

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“…Metallic as well as semiconducting behavior was found. [5][6][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.…”

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confidence: 98%

Epitaxy and magnetotransport ofSr2FeMoO6thin films

2000

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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...

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“…However, epitaxial growth was found to be complicated and difficult to control. There are indications that high structural quality of films grown on SrTiO 3 is associated with semiconducting behavior [7,8]. Here, we report on the epitaxial growth of Sr 2 CrWO 6 .…”

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Epitaxial growth and transport properties of Sr2CrWO6 thin films

Philipp

Reisinger

Schonecke

et al. 2003

Journal of Applied Physics

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We report on the preparation and characterization of epitaxial thin films of the double-perovskite Sr 2 CrWO 6 by Pulsed Laser Deposition (PLD). On substrates with low lattice mismatch like SrTiO 3 , epitaxial Sr 2 CrWO 6 films with high crystalline quality can be grown in a molecular layer-by-layer growth mode. Due to the similar ionic radii of Cr and W, these elements show no sublattice order. Nevertheless, the measured Curie temperature is well above 400 K. Due to the reducing growth atmosphere required for double perovskites, the SrTiO 3 substrate surface undergoes an insulator-metal transition impeding the separation of thin film and substrate electric transport properties. [5]. Thin films of the well studied system Sr 2 FeMoO 6 have been fabricated by pulsed-laser deposition (PLD) at relatively high temperatures of about 900 • C [6]. However, epitaxial growth was found to be complicated and difficult to control. There are indications that high structural quality of films grown on SrTiO 3 is associated with semiconducting behavior [7,8]. Here, we report on the epitaxial growth of Sr 2 CrWO 6 . Due to the good lattice match, epitaxial films of this material can be grown on SrTiO 3 substrates in a molecular layer-by-layer growth mode resulting in high crystalline quality.Sr 2 CrWO 6 thin films were deposited from stoichiometric targets [5] on atomically flat, HF etched and annealed (001) SrTiO 3 substrates by PLD using a 248 nm KrF excimer laser [9]. Fig. 1 shows the RHEED (Reflection High Energy Electron Diffraction) [10] intensity oscillations of the (0, 0) diffraction spot recorded during the PLD growth of a c-axis oriented Sr 2 CrWO 6 film. The molecular layer-bylayer or Frank-van der Merwe growth mode [11] is achieved for a substrate temperature of 740 • C, an argon pressure of 2 × 10 −4 Torr, a laser repetition rate of 2 Hz, and a laser energy density on the target of 1.2 J/cm 2 . RHEED was performed with 15 keV electrons at an incident angle of about 2 • . To obtain the number of RHEED oscillations per unit cell, the film thickness has been determined precisely by X-ray reflectometry (Fig. 4) and then divided by the number of observed RHEED oscillations. The derived molecular layer or block thickness corresponds to half a unit cell (c/2 = 4.004Å). Note that the intensity oscillations of the (0,0) and (0,1) spot are out of phase, since for the (0,1) spot the electrons reflected from different growth planes interfere constructively (in-Bragg condition). In this case no RHEED oscillations are expected. The fact that we do observe RHEED oscillations is caused by multiple and diffuse, incoherent scattering which results in an * Electronic address: Boris.Philipp@wmi.badw.de increasing (decreasing) intensity with increasing (decreasing) step density [12,13]. Figure 2 shows an in situ AFM picture of a 42 nm thick film. Clearly, a terrace structure due to the nonvanishing substrate miscut with about 4Å high steps corresponding to half a unit cell of Sr 2 CrWO 6 can be seen. The AFM analysis shows that Sr 2 CrW...

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Pulsed-laser-deposited epitaxial Sr2FeMoO6−y thin films: Positive and negative magnetoresistance regimes

Cited by 92 publications

References 22 publications

Hall effect of epitaxial double-perovskite Sr2FeMoO6 thin films

Hall effect of epitaxial double-perovskite Sr2FeMoO6 thin films

Epitaxy and magnetotransport ofSr2FeMoO6thin films

Epitaxial growth and transport properties of Sr2CrWO6 thin films

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