6 research outputs found
Quantum critical behavior induced by Mn impurity in CuGeO3
Results of high frequency (60-315 GHz) studies of ESR in CuGeO3 single
crystals containing 0.9% of Mn impurity are reported. Quantitative EPR line
shape analysis allowed concluding that low temperature magnetic susceptibility
for T <40 K diverges following power law with the critical exponent 0.81 and
therefore manifests onset of a quantum critical (QC) regime. We argue that
transition into Griffiths phase occurs at TG~40 K and disorder produced by Mn
impurity in quantum spin chains of CuGeO3 may lead to co-existence of the QC
regime and spin-Peierls dimerisation.Comment: 2 pages, submitted to SCES05 proceeding
Antiferro-quadrupole resonance in CeB6
We report experimental observation of a new type of magnetic resonance caused
by orbital ordering in a strongly correlated electronic system. Cavity
measurements performed on CeB6 single crystals in a frequency range 60-100 GHz
show that a crossing of the phase boundary TQ(B) between the
antiferro-quadrupole and paramagnetic phases gives rise to development at T
<TQ(B) of a magnetic resonance. The observed mode is gapless and correspond to
g-factor 1.62.Comment: 2 pages, Submitted to SCES05 proceeding
Magnetic resonance in cerium hexaboride caused by quadrupolar ordering
Experimental evidence of the magnetic resonance in the antiferro-quadrupole
phase of CeB6 is reported. We have shown that below orbital ordering
temperature a new magnetic contribution from localized magnetic moments (LMM)
emerge and gives rise to observed resonant phenomenon. This behaviour is hardly
possible to expect in dense Kondo system, where LMM should vanish al low
temperatures rather than emerge. From the other hand, in the quadrupole
ordering concept, where magnetism of Ce magnetic ions is solely accounted, is
difficult to explain splitting of magnetisation into components having
different physical nature. Therefore an adequate theory explaining magnetic
properties of CeB6 including magnetic resonance and orbital ordering appears on
the agenda.Comment: 4 pages, Accepted paper for MISM05 proceeding
Disorder driven quantum critical behavior in CuGeO3 doped with magnetic impurity
For the CuGeO3 doped with 1% of Fe the quantum critical behavior in a wide
temperature range 1-40 K is reported. The critical exponents for susceptibility
along different crystallographic axes are determined: a=0.34 (B//a and B//c)
and a=0.31 (B//b). New effect of the frequency dependence of the critical
exponent is discussed.Comment: Submitted to SCES0