72 research outputs found
Anisotropic magnetoresistive and magnetic properties of La_{0.5}Sr_{0.5}CoO_{3-\delta} film
The magnetic and transport properties of La_{0.5}Sr_{0.5}CoO_{3-\delta} film
grown on a LaAlO_3 substrate by pulsed-laser deposition are studied. The
properties are found to be influenced by the magnetic anisotropy and
inhomogeneity. Magnetoresistance anisotropy is determined by the shape
anisotropy of the magnetization and the strain-induced magnetic anisotropy due
to the film-substrate lattice interaction. Indications of the
temperature-driven spin reorientation transition from an out-of plane orderded
state at low temperatures to an in-plane ordered state at high temperatures as
a result of competition between the mentioned sources of magnetic anisotropy
are found.Comment: 5 pages, 8 figures, submitted to Fiz. Nizk. Temp, an extended version
of short communication in cond-mat/020734
Torque magnetometry studies of new low temperature metamagnetic states in ErNi_{2}B_{2}C
The metamagnetic transitions in single-crystal ErNiBC have been
studied at 1.9 K with a Quantum Design torque magnetometer. The critical fields
of the transitions depend crucially on the angle between applied field and the
easy axis [100]. Torque measurements have been made while changing angular
direction of the magnetic field (parallel to basal tetragonal -planes) in a
wide angular range (more than two quadrants). Sequences of metamagnetic
transitions with increasing field are found to be different for the magnetic
field along (or close enough to) the easy [100] axis from that near the hard
[110] axis. The study have revealed new metamagnetic states in ErNiBC
which were not apparent in previous longitudinal-magnetization and neutron
studies.Comment: 3 pages (4 figs. incl.) reported at 52th Magnetism and Magnetic
Materials Conference, Tampa, Florida, USA, November 200
Magnetoresistive study of antiferromagnetic--weak ferromagnetic transition in single-crystal LaCuO
The resistive measurements were made to study the magnetic field-induced
antiferromagnetic (AF) - weak ferromagnetic (WF) transition in LaCuO
single-crystal. The magnetic field (DC or pulsed) was applied normally to the
CuO layers. The transition manifested itself in a drastic decrease of the
resistance in critical fields of ~5-7 T. The study is the first to display the
effect of the AF -WF transition on the conductivity of the LaCuO
single-crystal in the parallel - to - CuO layers direction. The results
provide support for the 3-dimensional nature of the hopping conduction of this
layered oxide.Comment: 8 pages, 7 figures, RevTe
Transport, thermal and magnetic properties of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_2O_{10-\delta}, a magnetic superconductor
Resistivity, thermoelectric power, heat capacity and magnetization for
samples of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_{2}O_{10-\delta} were investigated in the
temperature range 1.8-300 K with a magnetic field up to 8 T. The resistive
transitions to the superconducting state are found to be determined by the
inhomogeneous (granular) structure, characterized by the intragranular, T_{c0},
and intergranular, T_{cg}, transition temperatures. Heat capacity, C(T), shows
a jump at the superconducting transition temperature T_{c0}\approx 37.5 K. A
Schottky-like anomaly is found in C(T) below 20 K. This low temperature anomaly
can be attributed to splitting of the ground term of paramagnetic
Gd^{3+} ions by internal and external magnetic fields.Comment: 3 pages (4 figs. incl.), reported at 50th Magnetism and Magnetic
Materials Conference, San Jose, CA, USA, 200
Influence of high-energy electron irradiation on the transport properties of La_{1-x}Ca_{x}MnO_{3} films (x \approx 1/3)
The effect of crystal lattice disorder on the conductivity and colossal
magnetoresistance in La_{1-x}Ca_{x}MnO_{3} (x \approx 0.33) films has been
examined. The lattice defects are introduced by irradiating the film with
high-energy (\simeq 6 MeV) electrons with a maximal fluence of about 2\times
10^{17} cm^{-2}. This comparatively low dose of irradiation produces rather
small radiation damage in the films. The number of displacements per atom (dpa)
in the irradiated sample is about 10^{-5}. Nethertheless, this results in an
appreciable increase in the film resistivity. The percentage of resistivity
increase in the ferromagnetic metallic state (below the Curie tempetature
T_{c}) was much greater than that observed in the insulating state (above
T_{c}). At the same time irradiation has much less effect on T_{c} or on the
magnitude of the colossal magnetoresistance. A possible explanation of such
behavior is proposed.Comment: RevTex, 22 pages, 3 Postscript figures, submitted to Eur. Phys. J.
Torque magnetometry studies of metamagnetic transitions in single-crystal HoNi_{2}B_{2}C and ErNi_{2}B_{2}C at T\approx 1.9 K
The metamagnetic transitions in single-crystal rare-earth nickel borocarbide
HoNi_{2}B_{2}C and ErNi_{2}B_{2}C have been studied at 1.9 K with a Quantum
Design torque magnetometer. The critical fields of the transitions depend
crucially on the angle between applied field and the easy axis [110] for
HoNi_2B_2C and [100] for ErNi_2B_2C. Torque measurements have been made while
changing angular direction of the magnetic field (parallel to basal tetragonal
ab-planes) in a wide angular range (more than two quadrants). The results are
used not only to check and refine the angular diagram for metamagnetic
transitions in these compounnds, but also to find new features of the
metamagnetic states. Among new results for the Ho borocarbide are the influence
of a multidomain antiferromagnetic state, and ``frustrated'' behavior of the
magnetic system for field directions close to the hard axis [100]. Torque
measurements of the Er borocarbide clearly show that the sequence of
metamagnetic transitions with increasing field (and the corresponding number of
metamagnetic states) depends on the angular direction of the magnetic field
relative to the easy axis.Comment: 3pages (4 figs. incl.) reported at 50th Magnetism and Magnetic
Materials Conference, San Jose, CA, USA, 200
- …