Journal of the Korean Physical Society

Korean Physical Society (한국물리학회)
권호 표지

Ferromagnetism Above Room Temperature in Cr-Doped AlN Films

Song, Young-Yeal;Yu, Seong-Cho;Lim, K. S;Quang, P. H;Yoo, Y. G.

  • Published : 20060000
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Abstract

Chromium-doped AlN .lms were prepared for a wide range of deposition parameters. The .lms were deposited on Si, Corning glass, and quartz substrates by magnetron sputtering. The single- phase .lms were obtained at an argon-nitrogen pressure of 6 mTorr for a substrate temperature range of 300 { 400 ±C. The .lms had typical thicknesses in the range of 200 { 1600 nm. The X-ray diraction pattern indicated a pure Cr-doped AlN phase. The concentration of Cr was deter- mined by using energy dispersive X-ray spectrometry (EDS) and X-ray photoemission spectrometry (XPS). The magnetization of the .lms grown on glass substrates was measured by using an alter- nating gradient magnetometer (AGM) system. The AGM data gave hysteresis loops with a small coercive force and a saturation magnetization, Ms of 0.1 emu/cm3. The Ms value is consistent with the literature values. The ferromagnetic resonance (FMR) spectra were measured from room temperature to 500 K at 9.2 GHz with the static .eld parallel to the .lm plane. The ferromagnetism was detected even at 500 K, which was the maximum temperature of our system. The optical ab- sorption gap determined by using Tsuc's method decreased from 6.18 eV to 4.74 eV with increasing Cr content from x = 0 to 0.25. This behavior can be attributed to the broadening of the impurity band, which is formed by the hybridization of p-d orbital. Transport properties were measured as a function of temperature from 77 K to 300 K by using the four-probe method. The data points satisfy the exponential law for variable range hopping in Cr doped AlN .lms.

Keywords

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