Growth and Characterization of Fept Compound thin Films
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dimpling and ion milling techniques and the microscopy was performed using a Philips 430ST TEM operating at 300 kV. XRD experiments were performed using Philips 3100 two-circle and Philips MRD four-circle diffractometers, with CuKY radiation in both cases. Magnetic and magneto-optic properties were measured using vibrating sample, magneto-optic Kerr and torque magnetometry (applied field = 20 kOe for torque measurements). The variation of Kerr rotation with incident photon energy was determined in an applied field of 20 kOe using a Nihon Kagaku Kerr spectrometer for photon energies 1.24-3.54 eV (1000 nm < X,_ 350 nm). RESULTS AND DISCUSSION Structural properties The effect of substrate temperature upon the resulting film structure is shown in Figure 1 for 100 nm thick FePt films deposited at 50 and 490 "C onto [001] MgO. Symmetric XRD data show the presence of substrate and alloy (002) peaks in both cases, but strong alloy (001) diffracted intensity only for the high deposition temperature film. This peak confirms the formation of ordered FePt since it is forbidden for all the constituents as well as the disordered alloy. Plan-view selected area electron diffraction patterns (SADP) from the film deposited at 50 'C confirm that this alloy adopts a chemically disordered cubic structure, indicating that low temperature formation is analogous to quenching from above the ordering temperature in the bulk material. No orientations other than are observed, indicating strong out-of-plane texture. For the film deposited at 490 'C the diffracted intensity on the low 20 side of the FePt (002) peak could be due to the Pt seed layer or either disordered or [100] oriented ordered FePt. Cross-section high resolution TEM (HRTEM) images, however, revealed that the Pt seed layer was not consumed during high temperature deposition and that no [ 100] FePt population was present. Symmetric XRD data from similar films grown with no Pt seed also show a complete absence of this diffracted intensity. The inset shows phi rocking curves from off-axis {111 } planes for both the MgO substrate and FePt 8
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Two Theta (deg) Figure 1. Symmetric x-ray diffraction data for 100 nm thick FePt alloy films deposited at 50 and 490 "C onto [001] MgO. The inset shows phi rocking curves from the {11I }planes of the MgO substrate and FePt film deposited at 490 "C. 92
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film deposited at 490 TC. The data show the four-fold symmetry expected for [001]
materials, and that there is no relative inplane rotation between the two, establishing the relationship FePt(110) II MgO(110). The same orientation was observed for the
film deposited at 50 "C. The effect of substrate choice upon the resulting film structure is established in Figure 2 which shows plan-view SADP for 100 nm thick FePt films deposited simultaneously onto [001] MgO (Figure 2a), [0001] A120 3 (Figure 2b) and amorphous SiO 2 (Figure 2c) at 490 "C. This is the same deposition for which data from the MgO sample are shown i
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