Determination of magnetic parameters in La0.7Sr0.3MnO3/SrTiO3 thin films using EMCD

Abstract

It is well known that the magnetic state of the La0.7Sr0.3MnO3 (LSMO) thin-film heterostructure is strongly correlated with the lattice, spin, orbital, and charge states, since these influence the electric and magnetic transport properties even on the unit-cell level. Therefore, understanding the material's magnetic properties on the nanoscale is important for the development of novel applications. The recently developed electron magnetic-circular dichroism (EMCD) technique allows the determination of atomic site-specific magnetic information via the use of transmitted electrons; however, its sensitivity is not high enough to quantitatively acquire magnetic information in many weak magnetism systems. Here, we utilized a dynamical diffraction-effect assisted EMCD technique to quantitatively determine the spin and orbital magnetic moment of LSMO/SrTiO3 thin films on the nanometer scale using a transmission electron microscope. Further, data processing was optimized to enhance the intensity of the EMCD signals for manganese, which have very weak magnetism at room temperature. High signal-to-noise ratio and accurate quantitative magnetic measurement are eventually achieved. Finally, the spin magnetic moments (0.73 ± 0.26 μB) are derived, and we also limited the ratio of the orbital to spin magnetic moment within an interval of (−0.03, 0.01). Our results not only present the nanoscale magnetic parameters of LSMO/SrTiO3, but also demonstrate how the measurement limit of the spin (or orbital) magnetic moment can be achieved, which is via the developed dynamical diffraction effect assisted EMCD technique.

Quantitative measurement of magnetic parameters by electron magnetic chiral dichroism

“…Even so, lots of efforts have been devoted to promote the development of the EMCD technique both in theoretical and experimental aspects in past years, such as the improvements of spatial resolution and signal-noise-ratio (SNR), [7][8][9]16,17] the fundamental understanding of its theory [18][19][20][21][22] and quantitative measurements of spin and orbital magnetic moments with elementspecificity and site-specificity. [23][24][25][26][27] Concerning the topic of this review, we summarize these issues for quantitative EMCD magnetic measurement as follows. First of all is the dynamical diffraction effects.…”

Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope

“…From the time of its discovery, EMCD has seen a continuous improvement in the signal to noise (S/N) ratio [5][6][7][8][9][10] , the spatial resolution [11][12][13][14][15][16] and the quantitative analysis. The technique has also been applied to explore material based questions such as interfacial magnetism 17,18 , magnetocrystalline anisotropy 19 , properties of dilute magnetic semiconductors 20 and rare earth magnets 21 . Recently EMCD signals with single atomic plane resolution were achieved 22,23 .…”

Electron energy-loss magnetic chiral dichroism of magnetic iron film affected by an underlayer in a double-layer structure

“…1 Since EMCD was first demonstrated by Schattschneider et al, 1 much effort has been made to develop it into a routine magnetic characterization technique in the transmission electron microscope (TEM). [4][5][6][7][8][9][10][11][12][13][14] Various EMCD experimental setups, for instance the energy spectrum imaging, 4,5 double aperture q À E mode, 6 spatially resolved EELS mode, 7 and scanning TEM, 8,9 have been proposed to improve the signal to noise ratio and the spatial resolution. In addition, the signal interpretation regarding the magnetic moment quantification has been widely concerned.…”

“…3,10,11 With a deep understanding of the dynamic diffraction, the quantification of element-specific and even site-specific orbital and spin moments has been experimentally realized. 11,12 Moreover, the theoretical simulation of the relative EMCD signal in various diffraction conditions has been widely applied for optimizing the experimental conditions 13,14 of EMCD or broadening its applications. 15 For the moment, the interpretation of quantitative results extracted from the EMCD signal is essentially based on an assumption that only one single-phase crystal is present in the electron beam path for each acquisition.…”

“…For instance, experiments were performed on a single crystal in polycrystalline materials of Fe, 9 Co, 16 Ni, 16 or their oxides 7,17 or on epitaxially grown thin layers of single-crystalline Fe, Mn, and their compounds observed from the cross-sectional view. 10,14,18,19 However, the assumption may fail if the EMCD technique is applied to other widely used systems such as core-shell structures, embedded nanoparticles, and multilayers observed along the out-of-plane direction. More than one material may present in the beam direction, considering that a complete removal of one component material in these composite structures may be difficult or possibly introduces changes in magnetic moments of other components.…”