Formation, characterization and magnetic properties of maghemite γ-Fe2O3 nanoparticles in borate glasses

•Fe and large-ion-radius elements (Y, Bi, Pb, and Sm) co-doped borate glasses were prepared.•Maghemite, γ-Fe2O3, nanoparticles arise in the glasses as a result of the thermal treatment.•The particles structure is the same for all large-ion-radius elements used.•The particle size depends on the large-ion-radius elements nature and concentration.•The glass magnetic properties correlate with the particles size.

A new type of nanocomposite materials based on maghemite, γ-Fe2O3, nanoparticles dispersed in borate glasses co-doped with low contents of iron together with the larger radius element combinations: Y and Bi, or Sm and Pb, or Y and Pb is studied. Nanoparticles arise as a result of heat treatment of the glasses which gives them properties characteristic of magnetically ordered substances. Transmission electron microscopy and XRD show that only one magnetic phase, namely γ-Fe2O3 nanoparticles, occurs in glasses subjected to the thermal treatment at 540 °C during 24 h independently on the doping element nature. At the same time doping element and their concentrations ratio in every combination affect the particles average size and glass magnetic properties, such as magnetization temperature dependences, Faraday rotation value and electron magnetic resonance spectrum characteristics.