5 research outputs found
Temperature and magnetic field dependence of the lattice constant in spin-Peierls cuprate CuGeO_3 studied by capacitance dilatometry in fields up to 16 Tesla
We present high resolution measurements of the thermal expansion coefficient
and the magnetostriction along the a-axis of CuGeO_3 in magnetic fields up to
16 Tesla. From the pronounced anomalies of the lattice constant a occurring for
both temperature and field induced phase transitions clear structural
differences between the uniform, dimerized, and incommensurate phases are
established. A precise field temperature phase diagram is derived and compared
in detail with existing theories. Although there is a fair agreement with the
calculations within the Cross Fisher theory, some significant and systematic
deviations are present. In addition, our data yield a high resolution
measurement of the field and temperature dependence of the spontaneous strain
scaling with the spin-Peierls order parameter. Both the zero temperature values
as well as the critical behavior of the order parameter are nearly field
independent in the dimerized phase. A spontaneous strain is also found in the
incommensurate high field phase, which is significantly smaller and shows a
different critical behavior than that in the low field phase. The analysis of
the temperature dependence of the spontaneous strain yields a pronounced field
dependence within the dimerized phase, whereas the temperature dependence of
the incommensurate lattice modulation compares well with that of the
dimerization in zero magnetic field.Comment: 25 pages, 15 Figs., to appear in Phys. Rev. B55 (Vol.5