Growth and Characterization of Epitaxial Thin Heterostructures of Ferromagnetic/Antiferromagnetic SrRuO 3 /Sr 2 YRuO 6
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69 Mat. Res. Soc. Symp. Proc. Vol. 602 © 2000 Materials Research Society
T10011 I.P_
Fig. I
Type I antiferromagnetic magnetic ordering inbulk Sr2YRuO6. (001) ferromagnetic sheets are coupled antiferromagnetically along [001].
and Y are located on the octahedral sites of the perovskite Sr 2 YRuO 6 crystal structure which has orthorhombic unit cell parameters a = 5.752A, b = 5.773A, and c = 8.158A. [2] Using these parameters, the pseudocubic lattice parameter is calculated to be 4.08A. Further studies show that bulk Sr 2YRuO 6 is not a metallic conductor and has an electrical resistivity of 5.9.104 Q-cm at 300K. [3] The reasons for choosing the conductive oxide SrRuO 3 for the ferromagnetic layer in the bilayer system are two-fold. SrRuO 3 thin films have a pseudocubic perovskite crystal structure and pseudocubic lattice parameter 3.905A, similar to Sr2YRuO 6. Also, structure and crystal quality studies have shown that single domain in-plane single crystal growth of SrRuO3 is possible on the smooth surface of SrTiO 3. Uniform growth can occur because of the small unit cell step height, 4A, of SrTiO 3 . [4] Therefore, SrRuO 3 has the potential for providing a good growth surface for Sr 2 YRuO 6 film growth with a very uniform interface between the Sr 2 YRuO 6 and SrRuO 3 layers. A high quality bilayer allows unprecedented control and optimization of exchange bias, an important phenomena in modem magnetic technology. EXPERIMENT The Sr 2YRuO 6 films were deposited on (001) SrRuO 3 substrates, miscut 0', 0.8', and 2° towards [100], by 900 off-axis sputtering using a stoichiometric target. The films were deposited at an operating pressure of 200mTorr (60%Ar/40%0 2) and temperature of 600°C. The samples were cooled to room temperature at an oxygen pressure of 300 Torr. The thickness of the films is approximately IOOOA. Thicker films, approximately 3000A, were deposited on the same substrate materials and under the same conditions except for an increased operating temperature of 700°C. The temperature was increased in an attempt to improve crystalline quality, but similar results for the two different films showed that this temperature change was not very significant. X-ray diffraction analysis, 0-20 scans and ý scans, was used to characterize crystallographic orientation and domain structure and sensitive magnetic measurements were made with the SQUID magnetometer.
RESULTS The Sr 2YRuO 6 films were deposited on (001) SrTiO 3 substrate samples that are miscut towards [100]. The rocking curve FWHM values ranging from 0.55070 to 70
0.60250 showed that the films had high crystalline quality. The out-of-plane lattice parameter of 4.05A is determined from the x-ray diffraction 0-20 scan of Sr 2YRuO 6 film on 20 miscut (001) SrTiO 3 substrate, as shown in Figure 2, which shows the film peaks at 21.97' for the (110) reflection and at 44.80' for the (220) reflection. This value is similar to the pseudocubic lattice parameter of bulk Sr 2YRuO 6 (4.08A). Therefore, incoherent growth occurs. Azimuthal x-ray scans of the off-ax
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