ANOMALOUS HALL RESISTIVITIES OF SINGLE-CRYSTAL FE16N2 AND FE-N MARTENSITE FILMS EPITAXIALLY GROWN BY MOLECULAR-BEAM EPITAXY

The anomalous and ordinary Hall resistivities for Fe16N2 (saturation m agnetization 4 pi M-s: 29 kG at room temperature) and Fe-N martensite (24.8 kG) films have been measured in the temperature range from 30 to 300 K and compared with pure Fe (21 kG) films. All films were epitaxi ally grown on GaAs(001) substrates by molecular beam epitaxy. The satu ration anomalous Hall resistivity rho(AS) for Fe16N2 at 300 K was 4.0x 10(-7) V cm/A which was much higher than the values for Fe-N martensit e (1.9X10(-7) V cm/A) and Fe (1.5X10(-7) V cm/A). Also the anomalous H all constant R-A at 300 K for Fe16N2 was 1.5X10(-11) V cm/A G, which w as much higher than the values for Fe-N martensite (0.8X10(-11) V cm/A G) and Fe (0.7x10(-11) V cm/A G). Such results are consistent with a much larger magnetic moment for Fe16N2. To investigate the consequence s of the giant magnetic moment for Fe16N2 as compared with Fe-N marten site and Fe, the temperature dependences of rho(AS) and R-A were measu red. The values of rho(AS) and R-A decreased monotonically with decrea sing temperature for Fe16N2, Fe-N martensite and Fe. In the temperatur e range from 30 to 300 K, the rho(AS) value for Fe16N2 was much higher than the values for Fe-N martensite and Fe. This originated from the larger thermal fluctuation of the magnetization for Fe16N2. The striki ng features of Fe16N2 magnetism were its giant magnetic moment and its large thermal fluctuation of the magnetic moment. The electrical resi stivity at room temperature for Fe16N2 was around 30 mu Omega cm as co mpared with 10 mu Omega cm for Fe. The difference was due mainly to th e difference in the residual resistivities. The electrical resistivity for Fe16N2 decreased monotonically with decreasing temperature, which is normal for a metallic material. (C) 1998 American Institute of Phy sics. [S0021-8979(98)07415-5].