Magnetic reversal processes of a FePt/α-Fe/FePt trilayer system with in-plane easy axes have been investigated within a micromagnetic approach. It is found that the magnetic reversal process consists of three steps: nucleation of a prototype of domain wall in the soft phase, the evolution as well as the motion of the domain wall from the soft to the hard phase and finally, the magnetic reversal of the hard phase. For small soft layer thickness L s , the three steps are reduced to one single step, where the magnetizations in the two phases reverse simultaneously and the hysteresis loops are square with nucleation as the coercivity mechanism. As L s increases, both nucleation and pinning fields decrease. In the meantime, the single-step reversal expands to a standard three-step one and the coercivity mechanism changes from nucleation to pinning. The critical thickness where the coercivity mechanism alters, could be derived analytically, which is found to be inversely proportional to the square root of the crystalline anisotropy of the hard phase. Further increase of L s leads to the change of the coercivity mechanism from * †
(110)-Oriented manganite thin films are essential for studies on the interface effects concerning spin-polarized electron injection, especially the proximity effect with high temperature superconducting cuprates. However, due to the peculiarity of the (110) plane, an atomically smooth surface generally can only sustain up to a quite low film thickness. Therefore, anisotropy along the two crystallographically asymmetric [001] and [11¯0] in-plane directions in ultrathin (110)-oriented manganite films are worthy of a careful investigation. Here, studies on the magnetotransport anisotropy of (110)-oriented epitaxial La2/3Ca1/3MnO3 (LCMO) thin films of 20 nm thickness grown by pulsed laser deposition are reported. Both SrTiO3 (STO) and LaAlO3 (LAO) substrates were adopted to highlight the lattice-misfit-strain effects. While in LCMO/STO film, the magnetic easy axis is along the [11¯0] direction, in LCMO/LAO film the [001] direction is easier. Accordingly, the resistivity and magnetoresistance measured along the easy axes are lower. The correlation between the magnetic and transport anisotropy then has been undoubtedly demonstrated. For the LCMO films on STO, property evolutions with temperature and magnetic field are free from fine features, and thus clear and easily understood, making STO a more appropriate substrate for interface studies in (110)-oriented heterostructures.
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