Disorder effects in epitaxial thin films of (La,Ca)MnO3

Abstract

We have investigated as-grown sputtered films of La0.7Ca0.3MnO3 in a thickness range between 5 and 200 nm on SrTiO3 substrates. The films are epitaxial, strained, and smooth. All films order magnetically around 175 K. Very thin films show full magnetization at low temperatures, but the temperature of the metal–insulator transition is appreciably lower than the magnetic ordering temperature. In thick films, the magnetization is much lower than expected. Both effects are probably related to structural disorder as found by transmission electron microscopy.

Transmission electron microscopy study of epitaxial La0.8MnO3thin films on SrTiO3

“…However, Aarts et al [13] reported that the type of oriented domains is dependant on the film thickness. As the film thickness increased from 5nm to more than 30nm, the microstructure of films turned from pure [001] oriented from mixed domains of…”

“…So the columnar grain size is larger in the film deposited at 1073K than at 873K, which is consistent with the results reported by Wang et al [11,12]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 The formation of oriented domains of Pnma structure has been largely reported not only in La 1-x R x MnO 3 (R= Ca, Sr or vacancy) thin films [13][14][15][16][17][18][19][20][21][22][23][24][25], but also reported in A 1-x R x MnO 3 ( A=Pr or La; B= Sr or Ca) bulk materials [26,27].…”

“…[9][10][11][12][13] Transmission electron microscopy (TEM) is a powerful tool for characterization of microstructures in materials. In the past few years TEM has been widely applied in the studies of CMR materials, and particularly in thin films of external-doped lanthanum manganites [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Van Tendeloo et al [15] Figure 1 shows the low magnification TEM images taken from the crosssectional samples of the two films.…”

Domain structures and superdislocations of La0.7Ca0.3MnO3 thin films grown on SrTiO3 substrates

“…Although there have many reports from domain-structure investigations in LCMO bulk and thin films [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] , superdislocations are seldom mentioned, and to our knowledge, were only observed in ordered alloys. 22 In this work, by means of using Bragg-diffraction contrast and high-resolution transmission electron microscopy, we investigated in detail the domains and dislocations of LCMO thin films deposited by pulsed laser on SrTiO 3 substrates.…”

“…The colossal magnetoresistance (CMR) manganite materials La 1-x Ca x MnO 3 , especially their thin films, have been extensively explored in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] because of their exciting potential practical applications and their interesting fundamental physics.…”