Es. Vlakhov et al., INFLUENCE OF THE SUBSTRATE ON GROWTH AND MAGNETORESISTANCE OF LA0.7CA0.3MNOZ THIN-FILMS DEPOSITED BY MAGNETRON SPUTTERING, Journal of applied physics, 83(4), 1998, pp. 2152-2157
Off-axis radio frequency magnetron sputtering was employed to grow La0
.7Ca0.3MnOz (LCMO) thin films onto three different types of substrates
. The substrate strongly influences the structure and the colossal mag
netoresistance effect of the obtained films. Single-crystalline thin f
ilms were prepared on LaAlO3 (100) substrates, showing a low value of
residual resistivity and a metal-insulator transition at a temperature
of up to T-peak=290 K. The latter value of the transition temperature
is one of the highest reported so far on thin films of the La-Ca-Mn-O
system. Films deposited onto Y-stabilized ZrO2 substrates and onto Mg
O substrates are polycrystalline and less textured. These films are ch
aracterized by a large negative magnetoresistance ratio MR=[R(H)-R(0)]
/R(0) measured for small values of the magnetic field H. For H = 1.5 k
Oe, the MR was found to be approximately - 30%, - 20%, and - 8% at tem
peratures of 20, 77, and 180 K, respectively. The magnetoresistance of
polycrystalline LCMO films shows two contributions, a low-field MR an
d a high-field MR, which are different in their dependence on temperat
ure. The low-field MR is related to the magnetization process and can
be attributed to scattering processes in domain walls or to tunneling
of polarized charge carriers between the grains of the polycrystalline
films. (C) 1998 American Institute of Physics.