Abstract
La0.7Ca0.3MnO3 (LCMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] single crystal substrates have been prepared by high magnetic field assisted pulsed laser deposition (HMF-PLD) developed by ourselves. Uniformly sized and vertically aligned nanorod structures can be obtained under an applied high magnetic field above 5 T, and the dimension size of the nanorods can be manipulated by varying the applied magnetic field. It is found that the magnetic anisotropy is strongly correlated to the dimension size of the nanorods. A significantly enhanced low-field magnetoresistance (LFMR) of −36% under 0.5 T at 100 K can be obtained due to the enhanced carrier scattering at the vertical grain boundaries between the nanorods for the LCMO films. The growth mechanism of the nanorods has been also discussed, which can be attributed to the variation of deposition rate, adatom surface diffusion, and nucleation induced by the application of a high magnetic field in the film processing. The successful achievements of such vertical nanorod structures will provide an instructive route to investigate the physical nature of these nanostructures and achieve nanodevice manipulation.
Highlights
Grain boundaries, there are only a few routes to control and manipulate the size of vertical nanostructures, such as phase ratio, growth rate, and so on, which require sophisticated technology and stringent fabrication conditions and have been recognized as a hard-attainable issue
The derived LCMO thin films were characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM)
Vertical aligned LCMO nanorod thin films have been obtained by high magnetic field assisted pulsed laser deposition method developed by ourselves, and the nanostructure nature of the LCMO films has been investigated
Summary
Grain boundaries, there are only a few routes to control and manipulate the size of vertical nanostructures, such as phase ratio, growth rate, and so on, which require sophisticated technology and stringent fabrication conditions and have been recognized as a hard-attainable issue. Our results show that uniformly sized, vertically aligned and one-dimensional nanorod structures can be obtained under a high magnetic field above 5 T. The LCMO films were deposited on (001) oriented LSAT single crystal substrates under various high magnetic fields. The selection of LSAT substrate is attributed to the small lattice mismatch (–0.2%) between the bulk and the substrate, and vertically aligned nanorod structures are almost impossible to be obtained in PLD processing without magnetic field due to the small derived strain[27], which is confirmed in our experiments. The successful achievement of nanorod structures in such small lattice mismatch will provide a unique route to tune the nanostructures in the thin films on substrates with small lattice mismatch, which is impracticable in PLD processing without a magnetic field. The applied magnetic fields in deposition process are denoted as HD, and the measured magnetic fields in magnetic property measurement are denoted as HM
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