Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 11: CE: Low-dimensional Systems - Materials 2
TT 11.10: Talk
Tuesday, March 23, 2010, 12:00–12:15, H18
Ferromagnetic zigzag chains in CdVO3: the role of cadmium — •Alexander Tsirlin and Helge Rosner — Max-Planck Institute CPfS, Dresden, Germany
Most of the low-dimensional spin systems show antiferromagnetic ground states or ground states with low net magnetization due to a weak asymmetry of the exchange couplings. Low-dimensional ferromagnets are rare, yet they show interesting low-temperature properties. These properties can be affected by quantum fluctuations, although entirely ferromagnetic systems with isotropic exchange couplings are not subject to the magnetic frustration. In this contribution, we present a band structure-based microscopic model for the low-dimensional spin-1/2 compound CdVO3. The crystal structure of CdVO3 shows zigzag chains of VO5 square pyramids. These chains can be considered as spin chains with nearest-neighbor (J1) and next-nearest-neighbor (J2) couplings, both being ferromagnetic: J1≃ J2≃ −50 K. Moreover, the interchain couplings are also ferromagnetic and lead to ferromagnetic ordering at TC=24 K. From the structural point of view, the exclusively ferromagnetic couplings in CdVO3 are highly counter-intuitive. However, band structure calculations explain these couplings by an effect of low-lying Cd 5s states that mix with V 3d states and mediate hoppings between the half-filled V dxy and the empty V dxz,dyz orbitals. The severe violation of the conventional superexchange scenario should be a general feature of Cd-containing compounds and can be used for the design of new low-dimensional magnets.