Microwave response near zero magnetic field in transition-metal-doped silicate glasses

Abstract

A sharp microwave response centered at zero magnetic field was observed in manganese- and iron-doped Na2O–CaO–MgO–SiO2 glasses with phase opposite to the normal Mn+2 and Fe+3 paramagnetic signals. The response can be described as magneto-induced microwave conductivity in the dielectric glass that derives from spin-dependent charge migration within the first coordination sphere of the paramagnetic ion. In contrast to the spin-polarized tunneling in ferromagnets between different valence states of metals, the observed effect is due to spin-dependent tunneling that occurs in the vicinity of manganese or iron in diluted paramagnetic systems.