175 research outputs found
Evidence for the singlet-dimer ground state in an S = 1 antiferromag netic bond alternating chain
Susceptibility, ESR and magnetization measurements have been performed on si
ngle crystals of an S=1 bond alternating chain compound: [Ni(333-tet)(\mu-NO
_2)](ClO_4) (333-tet = N,N'-bis(3-aminopropyl)propane-1,3-diamine) and the c
ompound doped with a small amount of Zn. We observed an anomalous angular de
pendence in the Zn-doped sample. These behaviors are well explained by the m
odel based on the VBS picture for the singlet-dimer phase. The picture impli es
that the free spins of S=1 with a positive single-ion anisotropy are indu ced
at the edges of the chains without forming the singlet-dimer.Comment: RevTeX, 14pages (preprint.sty) with 5figures, submitted to Phys. R
ev. Let
Magnetization Plateaus in the Spin-1/2 Kagome Antiferromagnets: Volborthite and Vesignieite
The magnetization of two spin-1/2 kagome antiferromagnets, volborthite and
vesignieite, has been measured in pulsed magnetic fields up to 68 T. A
magnetization plateau is observed for each compound near the highest magnetic
field. Magnetizations at saturation are approximately equal to 0.40Ms for both
compounds, where Ms is the fully saturated magnetization, irrespective of a
difference in the distortion of the kagome lattice between the two compounds.
It should be noted that these values of magnetizations are significantly larger
than Ms/3 predicted theoretically for the one-third magnetization plateau in
the spin-1/2 kagome antiferromagnet. The excess magnetization over Ms/3 is
nearly equal to the sum of the magnetizations gained at the second and third
magnetization steps in volborthite, suggesting that there is a common origin
for the excess magnetization and the magnetization steps.Comment: 4 pages, 4 figures. Phys. Rev. B, accepte
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