scholarly journals Electrical resistance and magnetoresistance of highly oriented and polycrystalline La0.67Sr0.33MnO3/MgO(001) thin films

2015 ◽  
Vol 55 (2) ◽  
Author(s):  
Bonifacas Vengalis ◽  
Irina Černiukė ◽  
Andrius Maneikis ◽  
Antanas Kleopas Oginskis ◽  
Gražina Grigaliūnaitė-Vonsevičienė
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Grain Boundaries ◽  
Current Flow ◽  
Rf Magnetron Sputtering ◽  
Polycrystalline Structure ◽  
Spin Polarized ◽  
Field Dependent ◽  
Parallel Channels

La0.67Sr0.33MnO3 thin films exhibiting a highly (001)-plane oriented and polycrystalline structure with a variable amount of (011)-textured crystallites have been grown in situ by RF magnetron sputtering on crystalline MgO(001) substrates by changing deposition temperature from 550 to 800 °C. Competing contribution of grains and grain boundaries to resistivity and magnetoresistance of the films has been investigated at T = (78–330) K. A model based on two parallel channels of current flow across grain boundaries has been applied to explain coexistence of low (LFMR) and high field (HFMR) magnetoresistance effects in the polycrystalline films at low temperatures. The LFMR effect has been understood assuming tunnelling of spin-polarized carriers via magnetic field-driven tunnelling barriers formed naturally between neighbouring misoriented grains. Meanwhile, the HFMR phenomenon has been associated with magnetic field-dependent hopping of carriers via the intergrain regions with reduced carrier density. Importance of the phase separation phenomenon on possible inhomogeneity of the material at grain boundaries has been discussed.

Comparison Between In-situ Annealing and External Annealing For Barium Ferrite Thin Films Made by RF Magnetron Sputtering

2005 ◽  
Vol 875 ◽  
Author(s):  
A. R. Abuzir ◽  
W. J. Yeh
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
Saturation Magnetization ◽  
Barium Ferrite ◽  
Rf Magnetron Sputtering ◽  
Silicon Substrates ◽  
Axis Orientation ◽  
Average Value ◽  
Ferrite Thin Films

AbstractDue to their large magnetic anisotropy perpendicular to the film plane, barium ferrite thick films (BaFe12O19, or BaM) with c-axis orientation are attractive candidates for microwave applications [1,2]. Barium ferrite thin films on silicon substrates without under layer have been deposited under various conditions by RF magnetron sputtering. The structure of the as-grown films is amorphous. External annealing in air has been done at 950°C for ten minutes to crystallize the films. C-axis oriented thin films with squareness of about 0.87 and coercivity of about 3.8KOe are obtained.Thick BaM films with c-axis orientation are difficult to achieve with one single deposition. Multilayer technique looks promising to grow thick films [3]. The external annealing process is difficult to incorporate with the multilayer procedure. An in-situ annealing procedure has been developed to obtain films, which can be used as the basic component for future multilayer deposition. Barium ferrites are first magnetron sputtered on bare silicon substrates in Ar + O2 atmosphere at substrate temperature of 500-600°C, the deposition pressure was kept about 0.008 torr. After the deposition, the temperature of the substrate is immediately increased to about 860°C for ten minutes in 140 torr of argon (80%) and oxygen (20%) mixture of gas, which was introduced into the chamber without breaking the vacuum. With the in-situ process, c-axis oriented thin films of 0.88 squareness and coercivity value of about 4.3KOe are obtained.Both annealing methods seem to have the similar effect on the perpendicular squareness and coercivity at various film thicknesses. The average value of the saturation magnetization Ms obtained from the in-situ annealing using multilayer technique is higher than that of the external one. We have grown films up to 1.0 micron thickness using the multilayer technique, in which three layers of 0.3 μm thickness each are deposited until the final thickness is reached. After the deposition of each layer, it was in-situ annealed before starting the deposition of the next layer. With the multilayer technique, coercivity of about 3.5 KOe and average value of the saturation magnetization Ms of about 4.0 K Gauss is obtained.

Temperature and magnetic field dependent Raman study of electron-phonon interactions in thin films of Bi2Se3 and Bi2Te3 nanoflakes

2020 ◽  
Vol 101 (24) ◽  
Author(s):  
Sören Buchenau ◽  
Sarah Scheitz ◽  
Astha Sethi ◽  
John E. Slimak ◽  
Tomke Eva Glier ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Field Dependent ◽  
Raman Study

Mapping of local electronic properties in nanostructured CMR thin films by Scanning Tunneling Microscopy (STM) and Local Conductance Map (LCMAP)

2004 ◽  
Vol 838 ◽  
Author(s):  
Sohini Kar ◽  
Barnali Ghosh ◽  
L. K. Brar ◽  
M A. Paranjape ◽  
A. K. Raychaudhuri
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Grain Boundaries ◽  
Electronic Properties ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Colossal Magnetoresistive ◽  
Spatially Resolved ◽  
Temperature Scanning

ABSTRACTWe have investigated the local electronic properties and the spatially resolved magnetoresistance of a nanostructured film of a colossal magnetoresistive (CMR) material by local conductance mapping (LCMAP) using a variable temperature Scanning Tunneling Microscope (STM) operating in a magnetic field. The nanostructured thin films (thickness ≈500nm) of the CMR material La0.67Sr0.33MnO3(LSMO) on quartz substrates were prepared using chemical solution deposition (CSD) process. The CSD grown films were imaged by both STM and atomic force microscopy (AFM). Due to the presence of a large number of grain boundaries (GB's), these films show low field magnetoresistance (LFMR) which increases at lower temperatures.The measurement of spatially resolved electronic properties reveal the extent of variation of the density of states (DOS) at and close to the Fermi level (EF) across the grain boundaries and its role in the electrical resistance of the GB. Measurement of the local conductance maps (LCMAP) as a function of magnetic field as well as temperature reveals that the LFMR occurs at the GB. While it was known that LFMR in CMR films originates from the GB, this is the first investigation that maps the local electronic properties at a GB in a magnetic field and traces the origin of LFMR at the GB.

Investigating the magnetic field-dependent conductivity in magnetite thin films by modelling the magnetorefractive effect

2013 ◽  
Vol 26 (3) ◽  
pp. 036002 ◽  
Author(s):  
Chris S Kelley ◽  
James Naughton ◽  
Emma Benson ◽  
Ruth C Bradley ◽  
Vlado K Lazarov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Field Dependent ◽  
The Magnetic Field ◽  
Magnetorefractive Effect

HIGH QUALITY FULLY IN-SITU MgB2 THIN FILMS OBTAINED BY DC MAGNETRON SPUTTERING

2003 ◽  
Vol 17 (04n06) ◽  
pp. 779-784 ◽  
Author(s):  
M. G. MAGLIONE ◽  
F. CHIARELLA ◽  
R. DI CAPUA ◽  
R. VAGLIO ◽  
M. SALVATO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Magnetron Sputtering ◽  
Target Surface ◽  
Residual Resistivity ◽  
Precursor Film ◽  
Large Area ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio

MgB 2 thin films were grown in-situ at INFM- University of Naples by a magnetron sputtering technique in a UHV system (10-7 Pa) equipped with 3 focused 2′′ magnetron sources (a stoichiometric MgB 2 and metallic Mg and B targets by Superconducting Components Inc.). The substrates (sapphire or MgO) were placed "on axis" at 7 cm from the target surface on the surface of a molybdenum heater that could be operated up to 1000°C under vacuum. Best results were obtained codepositing MgB 2 and Mg at equal sputtering power (500W) for 10 min on cold substrates, resulting in a Mg rich Mg-B precursor film. The films were then annealed inhyphen;situ at 830°C for 10 min in a In sealed Nb box in presence of saturated Mg vapor. The process is highly reproducible and can be easily scaled to produce large area films. The resulting films were about 1μm thick, with 100nm surface roughness as measured by AFM Resistive transition showed a maximum T c of 35 K and a transition width lower than 0.5 K. The residual resistivity ratio was 1.6 for the best sample. Resistivity measurements in external magnetic field up to 8 T have been performed both in parallel and perpendicular configuration. The upper critical magnetic field vs. temperature behavior has been determined from the experimental data and the superconducting anisotropy has been calculated for samples with different T c .

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