Magnetic properties of nitric oxide molecules physisorbed into nano-sized pores of MCM-41

We physisorbed nitric oxide (NO) molecules with spin (S) of 1/2 into the nano-sized pores of the meso-porous medium MCM-41, which allows molecule adsorption of the multi-layer form. The adsorption and desorption isotherms were observed at 121.5 K, and the effects of adsorption efficacy (i.e., the filling ratio, n) on the magnetic properties were investigated. Changes in the condensation state in the temperature region of 100–120 K were observed through the magnetic measurements, and the resultant phase diagram against n resembled that obtained for the physisorption of oxygen (O2) molecules with S = 1. For T < 90 K, two NO molecules dimerized independently of n and diamagnetic dinitrogen dioxide (N2O2) was formed. The two-dimensional magnetic state, seen for O2 physisorption, was not observed in the present system, probably due to the prominent electric polarity of the NO molecule.