Local Temperature Measurement of Avalanche Front in Mn12-Acetate

Local magnetization measurements using micro-Hall bars have recently revealed that a magnetic avalanche propagates as a narrow front moving with subsonic speed. In analogy with chemical deflagration (or combustion), we have proposed ``magnetic deflagration,'' a thermodynamic process by which the reversing spins produce heat stimulating the reversal of neighboring spins in the crystal [1]. Based on this model, a simple calculation yields a ``flame front'' temperature of the order of 10 K or higher. Although it has been established that the average temperature exhibits a (small) increase, confirmation of this model requires local, fast measurements of the temperature of the front. We describe experimental progress using $\mu$m sized arrays of germanium thermometers. \newline \newline [1] Y. Suzuki, et. al., Phys. Rev. Lett. 95, 147201 (2005).