High-Field Magnetization Study of [Cu(pyz)₂(HF₂)]PF₆: An S = 1:2 Quasi-two-dimensional Heisenberg Magnet

We report on pulsed-field magnetization studies of the quasi-two-dimensional spin system [Cu(pyz)₂(HF₂)]PF₆. The magnetization saturates at B^ab _C = 37.5 T and B^c _C= 33.8 T for in-plane and out-of-plane orientations of the applied magnetic field, respectively. In addition, the angular dependence of the g-factor studied by electron-spin resonance reveals orbital overlap in the ab plane suggesting a quasi-two-dimensional square-lattice network of Cu spins. It is argued that the high-field behavior is governed by the two-dimensional nature of the spin correlations due to the large anisotropy of the exchange couplings.