μSR study of organic systems: ferromagnetism, antiferromagnetism, the spin-crossover effect, and fluctuations in magnetic nanodiscs

We present the results of recent μSR experiments on a variety of novel organic and molecular magnetic systems. Muons are sensitive to local static fields and magnetic fluctuations, but can probe much more than just the onset of long-range magnetic order. We review our work on nitronyl nitroxide organic ferromagnets and antiferromagnets. We describe a muon study of the spin-crossover phenomenon which has been studied in Fe(PM-PEA)2(NCS)2, and which shows Gaussian and root-exponential muon relaxation in the high-spin and low-spin phases, respectively. Experiments on a disc-shaped molecular complex containing Fe19 (with spin ((31)/(2))) reveal the effects of quantum tunneling of magnetization and allow an estimate of the quantum tunneling rate