85 research outputs found
Spin-stripe phase in a frustrated zigzag spin-1/2 chain
Motifs of periodic modulations are encountered in a variety of natural
systems, where at least two rival states are present. In strongly correlated
electron systems such behaviour has typically been associated with competition
between short- and long-range interactions, e.g., between exchange and
dipole-dipole interactions in the case of ferromagnetic thin films. Here we
show that spin-stripe textures may develop also in antiferromagnets, where
long-range dipole-dipole magnetic interactions are absent. A comprehensive
analysis of magnetic susceptibility, high-field magnetization, specific heat,
and neutron diffraction measurements unveils -TeVO as a nearly
perfect realization of a frustrated (zigzag) ferromagnetic spin-1/2 chain.
Strikingly, a narrow spin stripe phase develops at elevated magnetic fields due
to weak frustrated short-range interchain exchange interactions possibly
assisted by the symmetry allowed electric polarization. This concept provides
an alternative route for the stripe formation in strongly correlated electron
systems and may help understanding other widespread, yet still elusive,
stripe-related phenomena.Comment: accapted in Nature Communication
Spin frustration and magnetic ordering in theS=12molecular antiferromagnetfcc−Cs3C60
We have investigated the low-temperature magnetic state of face-centered-cubic (fcc) Cs3C60, a Mott insulator and the first molecular analog of a geometrically frustrated Heisenberg fcc antiferromagnet with S=1/2 spins. Specific heat studies reveal the presence of both long-range antiferromagnetic ordering and a magnetically disordered state below TN=2.2 K, which is in agreement with local probe experiments. These results together with the strongly suppressed TN are unexpected for conventional atom-based fcc antiferromagnets, implying that the fulleride molecular degrees of freedom give rise to the unique magnetic ground state
ESR of MnO embedded in silica nanoporous matrices with different topologies
Electron spin resonance (ESR) experiments were performed with
antiferromagnetic MnO confined within a porous vycor-type glass and within
MCM-type channel matrices. A signal from confined MnO shows two components from
crystallized and amorphous MnO and depends on the pore topology. Crystallized
MnO within a porous glass shows a behavior having many similarities to the
bulk. In contrast with the bulk the strong ESR signal due to disordered
"surface" spins is observed below the magnetic transition. With the decrease of
channel diameter the fraction of amorphous MnO increases while the amount of
crystallized MnO decreases. The mutual influence of amorphous and crystalline
MnO is observed in the matrices with a larger channel diameter. In the matrices
with a smaller channel diameter the ESR signal mainly originates from amorphous
MnO and its behavior is typical for the highly disordered magnetic system.Comment: 7 pages pdf file, 5 figure
Spin-Wave Description of Nuclear Spin-Lattice Relaxation in Mn_{12}O_{12} Acetate
In response to recent nuclear-magnetic-resonance (NMR) measurements on the
molecular cluster Mn_{12}O_{12} acetate, we study the nuclear spin-lattice
relaxation rate 1/T_1 developing a modified spin-wave theory. Our microscopic
new approach, which is distinct from previous macroscopic treatments of the
cluster as a rigid spin of S=10, not only excellently interprets the observed
temperature and applied-field dependences of 1/T_1 for ^{55}Mn nuclei but also
strongly supports the ^{13}C NMR evidence for spin delocalization over the
entire molecule.Comment: to be published in Phys. Rev. Lett., 4 pages, 4 figures embedde
Multiferroic FeTeOBr: Alternating spin chains with frustrated interchain interactions
A combination of density functional theory calculations, many-body model
considerations, magnetization and electron spin resonance measurements shows
that the multiferroic FeTeOBr should be described as a system of
alternating antiferromagnetic chains with strong Fe-O-Te-O-Fe bridges
weakly coupled by two-dimensional frustrated interactions, rather than the
previously reported tetramer models. The peculiar temperature dependence of the
incommensurate magnetic vector can be explained in terms of interchain exchange
striction being responsible for the emergent net electric polarization.Comment: 7 pages, 6 figure
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