8,573 research outputs found
Current-driven magnetization decrease in single crystalline ferromagnetic manganese oxide
The electrical and magnetic response to a bias current has been investigated
in a singlecrystalline ferromagnetic manganese oxide
CaMnO . A significant decrease of the magnetization is
observed at the same threshold current where a non-linearity of V-I
characteristics appears. Such a behavior cannot be understood in the framework
of the filamentary picture usually invoked for the non linearity of the other
manganese oxides. Instead, an analogy with spintronic features might be useful
and experimental signatures seem to be in agreement with excitations of spin
waves by an electric current. This provides an example of a bulk system in
which the spin polarized current induces a macroscopic change in the
magnetization.Comment: 3 pages, 4 figure
Magnetocaloric effect and improved relative cooling power in (La0.7Sr0.3MnO3/SrRuO3) superlattices
Magnetic properties of a series of (La0.7Sr0.3MnO3/SrRuO3) superlattices,
where the SrRuO3 layer thickness is varying, are examined. A room-temperature
magnetocaloric effect is obtained owing to the finite size effect which reduces
the TC of La0.7Sr0.3MnO3 layers. While the working temperature ranges are
enlarged,, -DeltaSmax values remains similar to the values in polycrystalline
La0.7Sr0.3MnO3. Consequently, the relative cooling powers are significantly
improved, the microscopic mechanism of which is related to the effect of the
interfaces at La0.7Sr0.3MnO3/SrRuO3 and higher nanostructural disorder. This
study indicates that artificial oxide superlattices/multilayers might provide
an alternative pathway in searching for efficient room-temperature magnetic
refrigerators for (nano)microscale systems.Comment: 14^pages, 3 figures, Submitted to J. Phys. Cond. Ma
Diluted manganese on the bond-centered site in germanium
The functional properties of Mn-doped Ge depend to large extent on the lattice location of the Mn impurities. Here, we present a lattice location study of implanted diluted Mn by means of electron emission channeling. Surprisingly, in addition to the expected substitutional lattice position, a large fraction of the Mn impurities occupies the bond-centered site. Corroborated by ab initio calculations, the bond-centered Mn is related to Mn-vacancy complexes. These unexpected results call for a reassessment of the theoretical studies on the electrical and magnetic behavior of Mn-doped Ge, hereby including the possible role of Mn-vacancy complexes
Metal-to-insulator crossover and pseudogap in single-layer compound BiSrCuO single crystals in high magnetic fields
The in-plane and the out-of-plane
magneto-transport in magnetic fields up to 28 T has been investigated in a
series of high quality, single crystal, hole-doped La-free Bi2201 cuprates for
a wide doping range and over a wide range of temperatures down to 40 mK. With
decreasing hole concentration going from the overdoped (p=0.2) to the
underdoped (p=0.12) regimes, a crossover from a metallic to and insulating
behavior of is observed in the low temperature normal state,
resulting in a disorder induced metal insulator transition. In the zero
temperature limit, the normal state ratio of the
heavily underdoped samples in pure Bi2201 shows an anisotropic 3D behavior, in
striking contrast with that observed in La-doped Bi2201 and LSCO systems. Our
data strongly support that that the negative out-of-plane magnetoresistance is
largely governed by interlayer conduction of quasiparticles in the
superconducting state, accompanied by a small contribution of normal state
transport associated with the field dependent pseudogap. Both in the optimal
and overdoped regimes, the semiconducting behavior of persists even
for magnetic fields above the pseudogap closing field . The method
suggested by Shibauchi \textit{et al.} (Phys. Rev. Lett. \textbf{86}, 5763,
(2001)) for evaluating is unsuccessful for both under- and overdoped
Bi2201 samples. Our findings suggest that the normal state pseudogap is not
always a precursor of superconductivity.Comment: 11 pages, 8 figures, published in PRB Nov 200
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