Magnetic properties of a spin-2 antiferromagnet with metal-radical hybrid spins

We present an S =2 antiferromagnet composed of a Mn-verdazyl complex [Mn (hfac_{) 2}] [o -Py -V -(4_{-F ) 2}] . An analysis of the magnetic behavior reveals that the strong antiferromagnetic intramolecular interaction between spins on Mn^{2 +} and the verdazyl radical forms an S =2 hybrid spin below approximately 100 K. In the low-temperature regions, the magnetic susceptibility and the specific heat indicate a phase transition to the three-dimensional order of the S = 2 system. Below the transition temperature, the magnetization curve exhibits a metamagnetic phase transition. From the analysis of electron spin resonance modes, we evaluate the on-site biaxial anisotropy responsible for the anisotropic magnetic behavior.