Effects of La Doping on CaB6 Thin Films Prepared by DC Magnetron Sputtering

doi:10.15541/jim20160464

Abstract

Abstract:

Both La doped and undoped Ca_1-_xLa_xB₆ (x = 0, 0.01, 0.02, 0.03) thin films were prepared by direct current magnetron sputtering method. Morphology and thickness of these films were characterized by atomic force microscopy. Thicknesses of doped films were about twice that of the undoped films, while the grain growth of the film was much enhanced by La doping. X-ray photoelectron spectroscopy (XPS) was used for investigating the chemical composition of film surfaces. Calculated La/Ca atomic ratios were close to the theoretical values, and there were no other ferromagnetic impurities or elements especially iron existing in films. Ca_0.98La_0.02B₆ films exhibited the highest room temperature saturation magnetization 84.54 emu/cm³. The saturation magnetization decreased with increasing film thickness. B₆ vacancies may be the main source of magnetism. Other defects such as grain boundaries also affected the magnitude of magnetism.

Key words: CaB6, thin film, La doping concentration, magnetism

CLC Number:

TB321

ZHANG Lin, LIU Hui-Hui, LIU Lin-Jia, ZHAO Guo-Qing, WU Yan, MIN Guang-Hui. Effects of La Doping on CaB₆Thin Films Prepared by DC Magnetron Sputtering[J]. Journal of Inorganic Materials, 2017, 32(5): 555-560.

Figures/Tables 7

Table 1 Atomic ratio in Ca1-xLaxB6 films

La doping concentration, x	Theoretical			Experimental
La doping concentration, x	B	Ca	La	B	Ca	La
0	6	1	0	5.11	1	0
0.01	6	0.99	0.01	5.43	0.99	0.0077
0.02	6	0.98	0.02	4.63	0.98	0.0160
0.03	6	0.97	0.03	5.07	0.97	0.0300

Fig. 1 Raman spectra of Ca1-xLaxB6 (x=0, 0.01, 0.02, 0.03) films

Fig. 2 (a) AFM surface morphologies, (b) FESEM images and (c) cross section morphologies of Ca1-xLaxB6 films deposited for 60 min

Fig. 3 (a) Film thickness, (b) bearing analysis and (c) Rq and Ra roughness of Ca1-xLaxB6 (x=0, 0.01, 0.02, 0.03) films In (b) and (c) films were deposited for 60 min

Fig. 4 The interface width σ of Ca1-xLaxB6films measured from AFM image versus deposition time and calculated values of the exponent β

Fig. 5 Room temperature magnetization curves for thick (t~ 1200 nm) and thin (t~20 nm) La doped CaB6 films [Oe=(1000/4π)A·m-1; emu·cm-3=4π×10-4 Wb·cm-3]

Fig. 6 Room temperature magnetization curves for Ca0.98La0.02B6 films with different sputtering times [Oe=(1000/4π)A·m-1; emu·cm-3=4π×10-4 Wb·cm-3]

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Effects of La Doping on CaB₆Thin Films Prepared by DC Magnetron Sputtering

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