https://doi.org/10.1140/epjb/e2010-10796-1
On the magnetism of Ln2/3Cu3Ti4O12 (Ln = lanthanide)
1
Experimental Physics V, Center for Electronic
Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
2
Resource Strategy, University of Augsburg, 86135 Augsburg, Germany
3
Solid State Chemistry, Martin-Luther
University Halle-Wittenberg, 06120 Halle, Germany
Corresponding author: a stephan.krohns@physik.uni-augsburg.de
Received:
18
October
2010
Revised:
15
December
2010
Published online:
1
February
2011
The magnetic and thermodynamic properties of the complete Ln2/3Cu3Ti4O12
series were investigated. Here Ln stands for the lanthanides La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb.
All the samples investigated
crystallize in the space group with lattice
constants that follow the lanthanide contraction. The lattice
constant of the Ce compound reveals the presence of Ce4+ leading to the composition Ce1/2Cu3Ti4O12. From
magnetic susceptibility and electron-spin resonance experiments
it can be concluded that the copper ions always carry a spin S = 1/2
and order antiferromagnetically close to 25 K. The Curie-Weiss
temperatures can approximately be calculated assuming a
two-sublattice model corresponding to the copper and lanthanide ions, respectively. It seems that the magnetic moments of the heavy rare earths are weakly coupled
to the copper spins, while for the light lanthanides no such coupling was found. The 4f moments remain paramagnetic down to the lowest temperatures, with the exception
of the Tm compound, which indicates enhanced Van-Vleck magnetism
due to a non-magnetic singlet ground state of the crystal-field
split 4f manifold. From specific-heat measurements we
accurately determined the antiferromagnetic ordering temperature
and obtained information on the crystal-field states of the
rare-earth ions.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011