ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
We report a systematic investigation of the fcc–bcc structural phase transition of thin Fe films sandwiched between CuNi alloys. The structures were of the type substrate/20 nm Pt/10 nm CuNi/0–2 nm Fe wedge/1 nm CuNi/2 nm Pt. All films were deposited in high vacuum by electron beam evaporation at temperatures ranging from 400 °C (Pt seed layer) to 100 °C (CuNi alloy layers and Fe wedge) to 20 °C (Pt cap layer). The CuNi composition ratio was varied in 10 at. % steps in order to vary its lattice constant from a=0.3607 nm (Cu) to 0.3517 (Ni) nm, which encompasses the value of gamma Fe (fcc low spin state). X-ray diffraction measurements reveal strong (111) texturing with an alignment of the Pt 〈111〉 axis better than 5 deg (rocking curve width) of the completed structures. Kerr loops in fields ±18 kOe were recorded as function of the Fe-wedge position with a spatial resolution of about 0.8 mm, corresponding to 0.1 nm Fe thickness resolution. These hysteresis loops reveal the saturation Kerr angle (0.1 mdeg resolution), the saturation field (anisotropy field) and a paramagnetic slope, which are all analyzed as function of the Fe thickness and the CuNi composition. Clear evidence for the formation of paramagnetic Fe is found for Cu-rich CuNi alloys, where a Kerr rotation below the resolution limit of our apparatus extends up to (approximately-greater-than)2 nm Fe thickness. The transition thickness from fcc to bcc Fe, as characterized by the onset of a linear uptake of the Kerr rotation, shows a pronounced maximum near about 25 at. % Ni, indicating that a small compression of the Fe lattice constant (about −2%) leads to the nonferromagnetic fcc Fe state. A similar study, using CuAu alloys with the aim of characterizing the high spin ferromagnetic fcc Fe phase, is in progress. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.361613
