In this work, measurement of the single-molecule magnet (SMM) spin state using a microstrip resonator is considered theoretically. An analysis of the SMM spin dynamics and the interaction between the microstrip and the SMM is presented. The interaction of the SMM with the microstrip causes a shift of the microstrip resonance frequency. An analytic expression for the maximum frequency shift is derived. For a spin-4 SMM Ni${}_4$, the maximum possible relative frequency shift is estimated to be $3.2\times {10}^{-5}$ for the excited state and $5.8\times {10}^{-5}$ for the ground state. The numerical analysis shows the hysteresis behavior of the resonator frequency. Two methods for measuring the spin state of the SMM with a microstrip resonator are proposed. One method is based on the sign of the frequency shift. The other one utilizes the hysteresis behavior of the resonator frequency.

• Received 21 July 2010

DOI:https://doi.org/10.1103/PhysRevB.84.024410