Principles and performance of a high-field time domain magnetic spectrometer

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Abstract
A time domain magnetic spectrometer based on a pick-up coil is presented for the study of spin-lattice relaxation rates in paramagnetic samples at high magnetic fields and at liquid-helium temperatures. The equilibrium between the spin system and the lattice is disturbed either by heating the spin system under the electron spin resonance condition (using far-infrared laser pulses) or by heating the lattice (using nonresonant laser pulses). Resulting magnetization changes induce a voltage in a pick-up coil oriented parallel to the field. By measuring the temporal evolution of this voltage, one can observe the spin-lattice relaxation directly. The spin-lattice relaxation in the diluted magnetic semiconductor CdMnTe is measured in order to demonstrate the performance of the spectrometer. The two methods of disturbing the equilibrium between the spin system and the lattice are compared.