The trilayer with CoMn (20 nm), Py (3.5 nm), and FeMn (5 nm) grown in the presence of magnetic field, . Also shown are the compensated spins of the CoMn AFM and the uncompensated Co spins at the CoMn-Py interface. Results indicated that caused a spin flop in the CoMn antiferromagnetic layer.
(a) Hysteresis loops for the as-grown bilayered samples, measured at 120 K after ZFC to 77 K. The CoMn-Py layer had its easy axis perpendicular to the growth field, while in the case of Py-FeMn, the EA was parallel to growth field. (b) EA vs variation for bilayers and trilayer showing for the CoMn-Py bilayer.
(a) EA and hard axis loops for the as-grown trilayer after ZFC, (b) effect of MFC from 473 to 120 K in −10 kOe with , (c) subsequent warming to rotate the EA to its ground position at 90°, and measurement after ZFC.
Position of the ground state EA (solid line) with respect to for the bilayered and trilayered samples: (a) the Py-FeMn bilayer with , i.e., the 0° position; (b) for the CoMn-Py sample, the EA was perpendicular to , i.e., the 90° position; and (c) the ground state EA was also at 90° for the trilayer.
Temperature variation in after MFC with . was measured at 0° and 90° while warming the sample. The 135° line was measured in a separate run, with the same MFC as previous. At 300 K, was applied at 90° rotating the EA to 135°. The sample was cooled and measured at 135° while warming.
(a) Stable EA created at 135° by applying a field at and ZFC to 120 K. (b) Effect of sharply oscillating and decreasing field and ZFC to 120 K.
XPEEM images of (a) magnetic contrast in the Py layer and (b) uncompensated Co spins in the CoMn of the CoMn-Py bilayer. (c) Magnetic domains in the Py of the CoMn-Py-FeMn trilayer. The Py and FeMn layers were 2 and 3 nm, respectively, to allow penetration of soft x rays to the bottom CoMn layer.
Schematic summary of the anisotropy states observed in the CoMn-Py-FeMn trilayer: (a) the as-grown state with randomly oriented local anisotropy axes and incoherence in Py moment orientations, (b) after MFC with applied perpendicular to making Py moments coherent and the EA (solid line) along , and (c) metastable state by keeping parallel to where the EA (dashed line) rotated when warmed above and became perpendicular to . This showed that the ground state of the EA was perpendicular to ; (d) thermally activated rotation of EA (dotted line) was assisted by applying a field for several seconds. The coherence of Py moments was partially broken by applying a sharply oscillating field and decreasing it to zero at . This returned the moments to a state resembling the frustration of the as-grown state (a).
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