On the magnetism of Ln{2/3}Cu{3}Ti{4}O{12} (Ln = lanthanide)

Abstract

The magnetic and thermodynamic properties of the complete Ln${}_{2/3}$Cu${}_3$Ti${}_4$O${}_{12}$ series were investigated. Here $Ln$ stands for the lanthanides La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. %Most of the compounds were prepared as single phase polycrystalline powder %without any traces of impurities. Marginal amounts of %impurities $(<2$ were detected $Ln=$ Gd, Er, and Tm. %Significant amounts of impurity phases were found for $Ln=$ Ce and Yb. All the samples investigated crystallize in the space group $Im\bar{3}$ with lattice constants that follow the lanthanide contraction. The lattice constant of the Ce compound reveals the presence of Ce${}^{4+}$ leading to the composition Ce${}_{1/2}$Cu${}_3$Ti${}_4$O${}_{12}$. 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. The heat-capacity results also revealed the presence of a small fraction of Ce${}^{3+}$ in a magnetic $4f^1$ state.

10 pages, 10 figures

References in corpus (6)

• Colossal dielectric constants in transition-metal oxides
• The multiferroic phases of (Eu:Y)MnO3
• Correlations of structural, magnetic, and dielectric properties of undoped and doped CaCu3Ti4O12
• Colossal dielectric constants: A common phenomenon in CaCu3Ti4O12 related materials
• On the magnetism of Ln{2/3}Cu{3}Ti{4}O{12} (Ln = lanthanide)
• Intermediate-valence behavior of the transition-metal oxide CaCu${}_3$Ru${}_4$O${}_{12}$

Cited by in corpus (2)

• On the magnetism of Ln{2/3}Cu{3}Ti{4}O{12} (Ln = lanthanide)
• Complex nature of magnetic field-induced ferroelectricity in GdCrTiO5