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

• Growth of α-Fe2O3 within nanochannels of Na-4 mica layered structure
• Generation of large compressive stress on the α-Fe2O3 nanfilms due to mismatch of thermal expansion coefficients of α-Fe2O3 and Na-4 mica
• Observation of Piezomagnetic effect in α-Fe2O3 by changing the measurement temperature
• The average values of Piezomagnetic constants extracted are in the range 2.3××10−6 to 3.4××10−4emu/gkg/cm2

α-Fe2O3 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-Fe2O3 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-Fe2O3. The values of piezomagnetic coefficient were estimated to be in the range 2.3××10−6 to 3.4××10−4emu/gkg/cm2. This is of the same order as that reported earlier by work carried out on single crystals of macrodimensions. Magnetization measurements of α-Fe2O3 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.