Novel features in the relaxation times of Mn12Ac

摘要: Abstract We report novel features of the relaxation time measured on single crystals a Mn12 acetate complex (Mn12Ac). Using SQUID magnetometer working at 100 mK and up to 8 T, we were able study magnetization low temperatures. For given temperature field, bulk sample can be described by one time, τ. When magnetic field is aligned along easy axis magnetization, observed deviate from thermal activation approximately 1.9 1.5 K for H = 0 1 T. Below this crossover temperature, tends saturate values around 107–108 s. A critical account will given, especially possibility quantum tunnelling.