Relation between damping, current-induced torques, and wall resistance for domain walls in magnetic nanowires

Abstract

We show that each mechanism of the Gilbert damping of wall motion corresponds to a current-induced drive torque on the domain wall, based on the same electron processes. For example, the damping theory of Heinrich, Fraitova, and Kambersky is directly related to the theory of ͑nonadiabatic͒ drive torques by Zhang and Li. Using momentum conservation, this relation is extended to the wall resistance. This leads to a classification of most existing electron theories of damping and drive torques, and of wall resistance, into only three different kinds. In all cases, the drive torque is derived from the damping torque by replacing the wall speed by an electron drift speed ӍR 0 j, where R 0 is the ordinary Hall constant and j the current density. This drift speed differs from the one which appears in existing theories of adiabatic spin-transfer torques on a wall. Using the present ideas, mechanisms for drive torques and wall resistance have been invented.

Wide ferromagnetic domain walls can host both adiabatic reflectionless spin transport and finite nonadiabatic spin torque: A time-dependent quantum transport picture

“…2(c) and 2(d)] means that most of spins are reflected [our convention is that positive I Sα i→i+1 (t) means spin-up along the αaxis moves from site i to i + 1], with I Sz 2→3 (t) → 0 around J sd w/γa 1. Such reflection is nonadiabatic effect, where previous studies have explored thereby generated force [2] on DW and its electrical resistance [2,8,[22][23][24][25][26][27]. Our time-dependent QT approach also reveals [Fig.…”

“…In spintronic experiments and applications, any deviation from adiabaticity of electron spin dynamics leads to fundamental effects, such as finite DW resistance [2,8,[22][23][24][25][26][27] and particularly important nonadiabatic [9,28] spin-transfer torque (STT) in electronic transport through DWs [3,4], skyrmions [5] and vortex cores [6,7]. The STT is a phenomenon [29] in which flowing electrons transfer spin angular momentum to local magnetization M(r) viewed as classical vector, as long as nonequilibrium spin expectation value of an electron and M(r) are noncollinear, as illustrated in Fig.…”

Synthesis and magnetic reversal of bi-conical Ni nanostructures

“…[9][10][11] While several theories have been proposed to explain the microscopic origin of STT in DW (Refs. [12][13][14] or DW magnetoresistance, 15,16 some fundamental questions still remain unclear.…”