摘要 : We report millimetre-wave electron spin resonance (ESR) measurements on single crystals of the high-spin molecules Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) and Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) within a temperature range of 1.4 K to 50 K... 展开 We report millimetre-wave electron spin resonance (ESR) measurements on single crystals of the high-spin molecules Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) and Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) within a temperature range of 1.4 K to 50 K and in magnetic fields of up to 5 Tesla. In our experiments it is possible to vary the orientation of the magnetic field with respect to the crystal axes, and thus to study the ESR lireshapes as a function of both temperature and angle. Our results confirm that Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) behaves as a single-molecule magnet with 5 = 15 and D = - 0.03 K, while Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) has S = 6 and D ~ 0.1 1C. A comparison of the experimental spectra with numerical simulations gives good agreement at low temperatures. At higher temperatures, we observe a nairowing of the ESR spectrum that is not explained by simple models. 收起