Speaker
Description
Current work is focused on the lattice subsystem of Cu(en)Cl 2 , Cu(tn)Cl 2 and
Cu(en)(H 2 O) 2 SO 4 (en = C 2 H 8 N 2 , tn = C 3 H 10 N 2 ), quasi-two-dimensional quantum magnets with
one-dimensional polymeric structure. Magnetic layers were described within spin = 1/2
Heisenberg models on the rectangular and zig-zag-square lattice with nearest-neighbor
couplings J 1 > J 2 . The largest spatial anisotropy R = 1-J 2 /J 1 and the strongest effect of
interlayer coupling J’ was observed in Cu(en)Cl 2 , while somewhat lower R and much weaker
J’ in Cu(tn)Cl 2 and Cu(en)(H 2 O) 2 SO 4 .
Specific heat in zero magnetic field was measured from 2 to 300 K and Raman spectra at 300
K. In Cu(en)Cl 2 and Cu(tn)Cl 2 , specific heat anomalies observed at 138 K and 160 K,
respectively, are associated with a structural phase transition. No structural phase transition
was observed in Cu(en)(H 2 O) 2 SO 4 . The contribution of acoustic modes is described within
Debye approximation with Debye temperatures Θ D = 147 K, 109 K and 93 K for
Cu(en)(H 2 O) 2 SO 4 , Cu(en)Cl 2 and Cu(tn)Cl 2 , respectively. The larger Θ D value of Cu(en)Cl 2
and the Raman shift towards higher energies correspond well with the Cu(en)Cl 2 specific heat
values which are lower than those of Cu(tn)Cl 2 in the whole temperature region. The influence
of acoustic modes on the magnetic correlations is discussed.
