1,950 research outputs found
Indication of antiferromagnetic interaction between paramagnetic Co ions in the diluted magnetic semiconductor ZnCoO
The magnetic properties of ZnCoO ( and 0.10) thin films,
which were homo-epitaxially grown on a ZnO(0001) substrates with varying
relatively high oxygen pressure, have been investigated using x-ray magnetic
circular dichroism (XMCD) at Co core-level absorption edge. The line
shapes of the absorption spectra are the same in all the films and indicate
that the Co ions substitute for the Zn sites. The magnetic-field and
temperature dependences of the XMCD intensity are consistent with the
magnetization measurements, indicating that except for Co there are no
additional sources for the magnetic moment, and demonstrate the coexistence of
paramagnetic and ferromagnetic components in the homo-epitaxial
ZnCoO thin films, in contrast to the ferromagnetism in the
hetero-epitaxial ZnCoO films studied previously. The analysis of
the XMCD intensities using the Curie-Weiss law reveals the presence of
antiferromagnetic interaction between the paramagnetic Co ions. Missing XMCD
intensities and magnetization signals indicate that most of Co ions are
non-magnetic probably because they are strongly coupled antiferromagnetically
with each other. Annealing in a high vacuum reduces both the paramagnetic and
ferromagnetic signals. We attribute the reductions to thermal diffusion and
aggregation of Co ions with antiferromagnetic nanoclusters in
ZnCoO.Comment: 21 pages, 7 figures, accepted for Physical Review
Non-Fermi-Liquid Scaling in Ce(Ru_{0.5}Rh_{0.5})_2Si_2
We study the temperature and field dependence of the magnetic and transport
properties of the non-Fermi-liquid compound Ce(Ru_{1-x}Rh_x)_2Si_2 at x=0.5.
For fields 0.1T the experimental results show signatures of the
presence of Kondo-disorder, expected to be large at this concentration. For
larger fields, however, magnetic and transport properties are controlled by the
coupling of the conduction electrons to critical spin-fluctuations. The
temperature dependence of the susceptibility as well as the scaling properties
of the magnetoresistance are in very good agreement with the predictions of
recent dynamical mean-field theories of Kondo alloys close to a spin-glass
quantum critical point.Comment: 4 pages, 4 figures. Improved discussion. To appear in Phys. Rev. Let
Soft x-ray magnetic circular dichroism study of weakly ferromagnetic ZnVO thin film
We performed a soft x-ray magnetic circular dichroism (XMCD) study of a
ZnVO thin film which showed small ferromagnetic moment. Field and
temperature dependences of V 2 XMCD signals indicated the coexistence of
Curie-Weiss paramagnetic, antiferromagnetic, and possibly ferromagnetic V ions,
quantitatively consistent with the magnetization measurements. We attribute the
paramagnetic signal to V ions substituting Zn sites which are somewhat
elongated along the c-axis
Photoemission and x-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)O thin films exhibiting photo-induced magnetization
By means of photoemission and x-ray absorption spectroscopy, we have studied
the electronic structure of (Ni,Zn,Fe,Ti)O thin films, which
exhibits a cluster glass behavior with a spin-freezing temperature of
K and photo-induced magnetization (PIM) below . The Ni and Zn
ions were found to be in the divalent states. Most of the Fe and Ti ions in the
thin films were trivalent (Fe) and tetravalent (Ti),
respectively. While Ti doping did not affect the valence states of the Ni and
Zn ions, a small amount of Fe ions increased with Ti concentration,
consistent with the proposed charge-transfer mechanism of PIM.Comment: 4 pages, 4 figure
A new double-layered kagome antiferromagnet ScFeGe
ScFeGe with the LiFeGe-type structure (space group
), which has a double-layered kagome lattice (18 site) of Fe
crystallographically equivalent to that of a well-known topological ferromagnet
FeSn, is newly found to be antiferromagnetic (AFM) with a high N\'eel
temperature of K, in contrast to the ferromagnetic
(FM) ground state previously proposed in a literature. Sc nuclear
magnetic resonance experiment revealed the absence of a hyperfine field at the
Sc site, providing microscopic evidence for the AFM state and indicating AFM
coupling between the bilayer kagome blocks. The stability of the AFM structure
under the assumption of FM intra-bilayer coupling is verified by DFT
calculations.Comment: 13 pages, 1 tables, 4 figure
Frustration-induced valence bond crystal and its melting in Mo3Sb7
121/123Sb nuclear quadrupole resonance and muon spin relaxation experiments
of Mo3Sb7 revealed symmetry breakdown to a nonmagnetic state below the
transition recently found at TS=50 K. The transition is characterized by a
distinct lattice dynamics suggested from narrowing of nuclear fields. We point
out that the Mo sublatice is a unique three-dimensional frustrated lattice
where nearest-neighbor and next-nearest-neighbor antiferromagnetic interactions
compete, and propose that tetragonal distortion to release the frustration
stabilizes long-range order of spin-singlet dimers, i.e., valence bond crystal,
which is thermally excited to the dynamic state with cubic symmetry.Comment: 4 pages. submitte
Interplay between quantum criticality and geometrical frustration in Fe3Mo3N with stella quadrangula lattice
In the eta-carbide-type correlated-electron metal Fe3Mo3N, ferromagnetism is
abruptly induced from a nonmagnetic non-Fermi-liquid ground state either when a
magnetic field (~14 T) applied to it or when it is doped with a slight amount
of impurity (~5% Co). We observed a peak in the paramagnetic neutron scattering
intensity at finite wave vectors, revealing the presence of the
antiferromagnetic (AF) correlation hidden in the magnetic measurements. It
causes a new type of geometrical frustration in the stellla quadrangula lattice
of the Fe sublattice. We propose that the frustrated AF correlation suppresses
the F correlation to its marginal point and is therfore responsible for the
origin of the ferromagnetic (F) quantum critical behavior in pure Fe3Mo3N
Itinerant electron magnetism of η-carbides Co6M6C and Ni6M6C (M=Mo and W)
Magnetic, transport, and thermal properties of metallic η-carbides Co6M6C and Ni6M6C (M = Mo and W) with the cubic Ni6Mo6C-type structure have been characterized. The Ni-based compounds Ni6Mo6C and Ni6W6C are Pauli paramagnets with temperature-independent susceptibilities. Susceptibilities of the Co-based compounds Co6Mo6C and Co6W6C are enhanced and temperature-dependent. Co6Mo6C remains paramagnetic down to the lowest temperature, while Co6W6C undergoes an antiferromagnetic-type transition at 46 K. A metamagnetic transition was observed for Co6W6C at 20–30 T at the lowest temperatures. The correlation among the enhancements in the susceptibility, the resistivity, and the electronic specific heat suggests the presence of moderate electron correlation in these compounds
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