Piezomagnetic behaviour in α-Fe2O3 nanofilms grown within nanochannels of Na-4 mica

Abstract α-Fe 2 O 3 nanofilms were grown within the 0.6 nm width nanochannels of sodium fluorophlogopite mica (Na-4 mica) structure. Due to a large difference in the values of thermal expansion coefficients of Na-4 mica and α-Fe 2 O 3 a huge compressive stress was generated on the latter as the composite was cooled from 1023 K to 300 K. Magnetization measurements on the composite as a function of temperature showed the presence of piezomagnetic effect in α-Fe 2 O 3 . The values of piezomagnetic coefficient were estimated to be in the range 2.3 × 10 −6 to 3.4 × 10 −4 emu / g kg / cm 2 . This is of the same order as that reported earlier by work carried out on single crystals of macrodimensions. Magnetization measurements of α-Fe 2 O 3 particles of diameter ~130 nm on the other hand, showed the usual behaviour viz., a magnetic phase transition from antiferromagnetic to ferromagnetic state at 237 K.