Trivalent-iron-doped andalusite as crystal for microwave waves

Paramagnetic ions Fe
³⁺
, substituted as an impurity in andalusite (Al
2
SiO
5
) host crystals, have been experimentally investigated. The spin-lattice relaxation and cross-relaxation times and inversion ratio in this spin system were observed. Dielectric properties of the host crystals were determined. General maser properties of trivalent-iron-doped andalusite crystal are discussed. Two types of the andalusite cavity masers are described. The
X
-band three-level maser operates at a temperature of 2.1°K and a magnetic field of 1400 gauss. Electronic gains of 25 dB and instantaneous bandwidth of 3.5 \pm 0.5 MHz, at the frequency of 9.45 GHz, were obtained. The
F
-band push-pull maser operates at a temperature of 2.1°K and a magnetic field of 2800 gauss. Electronic gains of 30 dB and instantaneous bandwidth of 5.5 ± 0.5 MHZ, at the frequency of 100.4 GHz, were obtained.