Orientation of the magnetic moments in a stack of 4 layers (0, 1, 2, 3), in which the magnetic moments in layers 0, 1, and 2 are coupled by the exchange interaction, thus building an exchange spring tri-layer; H is an external magnetic field directed antiparallel to the magnetization in layer 0; layer 3 is a ferromagnetic separated from layer 2 by a potential barrier that interrupts their exchange interaction, the magnetization directions of layers 0 and 3 being fixed and antiparallel; the magnetoresistance of the stack is normal, being mainly determined by the magnetization direction of layer 2 with respect to the one of layer 3.
(Color online) Current-voltage characteristics (IVC) of the magnetic stack from Fig. 1 calculated for , , , , and . Branches 0 – b and a – a′ of the IVC correspond to parallel and antiparallel orientations of the magnetization of layers 0 and 2, respectively (parts 0 – a′ and b – b are unstable); branch a – b corresponds to the tilt of the magnetization of layer 2 with respect to that of layer 0 (that is, ).
(Color online) The angle , which describes the tilt of the direction of the magnetization in layer 2 with respect to layer 0 as a function of the current in the current-biased regime. The curve was calculated for , , 0.36, and .
Equivalent circuit for a Joule-heated magnetic stack of the type shown in Fig. 1. A resistance, , biased by a fixed DC current, , is connected in parallel with a capacitor C; and R rst are the angle-dependent resistance of the stack and the resistance of the rest of the circuit, respectively; and I c are the currents flowing through the stack and the capacitor, respectively.
(Color online) Spontaneous oscillations of the current through the stack, I s (t), and the voltage drop across it, V(t), calculated for , , and ; and . I s (t) and V(t) develop from the initial state toward the limiting cycle shown by the thick solid line, along which they execute a periodic motion. The stationary IVC of the stack is shown by the thin solid line.
(Color online) Spontaneous oscillations of the magnetization direction angle, , associated with the periodic motion of I s (t) and V(t) along the limiting cycle shown in Fig. 5; τ0 is the characteristic evolution time of the current . Calculations are made for , 0.36, and .
(Color online) Spontaneous oscillations of current through the stack, I s (t), and voltage, V(t), calculated for , , and . I(t) and V(t) develop toward the limit cycle (thick solid line) from the initial state, which can be either inside or outside it, and execute a periodic motion along the limit cycle. The stationary IVC of the stack is shown as a thin solid line.
(Color online) Spontaneous oscillations of the magnetization direction angle, , associated with the periodic motion of I s (t) and V(t) along the limiting cycle shown in Fig. 7; τ0 is the characteristic evolution time of the current . Calculations are made for , , and .
(Color online) (a) Schematic of the studied material system: two ferromagnets, FM 1 and FM 2, each exchange pinned by an antiferromagnet, AFM 1 and AFM 2, are separated by a non-magnetic alloy, NM. The middle and right panels illustrate two methods to alter the exchange pinning such that the magnetization of the two ferromagnets become antiparallel. T B is the antiferro-antiferromagnetic blocking temperature and is the coercive field of the ferromagnets. (b) and (c) are minor magnetoresistance loops before and after the field-heat treatment, respectively. Arrows indicate the magnetization direction in FM 1 and FM 2.
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