Laser-induced magnetization switching in films with perpendicular anisotropy: A comparison between measurements and a multi-macrospin model

Abstract

Thermally assisted ultrafast magnetization reversal in a dc magnetic field in magnetic multilayer thin films with perpendicular anisotropy has been investigated in the time domain using femtosecond laser heating. The experiment is set up as a stroboscopic optical time resolved magneto-optical Kerr effect magnetometer. It is observed that a modest laser fluence of about 0.3 mJ/ cm 2 induces switching of the magnetization in an applied field much less than the dc coercivity ͑0.8 T͒ on the subnanosecond time scale. This switching was thermally assisted by the energy from the femtosecond pump pulse. The experimental results are compared with a model based on the Landau-Lifshitz-Bloch equation. The comparison supports a description of the reversal process as an ultrafast demagnetization and partial recovery followed by slower thermally activated switching due to the spin system remaining at an elevated temperature after the heating pulse.

Fast magnetization precession observed in L1-FePt epitaxial thin film

“…This recovery rate depends not only on materials but also on the underlying nanostructure, pump-laser fluence, and other factors; thus, this process is not easily modeled. 5,[14][15][16] Here, we assume that the oscillation signals can be fitted to a damped-harmonic function added to an exponential-decaying background that is characterized by several time-independent parameters; specifically, we have a + b exp͑−t͒ + c sin͑2ft + ͒exp͑−t / ͒, where a and b are the background magnitudes and is the background recovery rate. Parameters c, f, , and are the amplitude, frequency, phase, and relaxation time of magnetization precession, respectively, as used previously.…”

“…2 Thus, there have been lots of studies not only on fundamental properties but also on advanced applications of magnetic storage 3 and memory devices 4 using these alloys. In the recording process, memory can be written by various means, such as with magnetic fields with or without assistance by laser heating 3,5 or microwaves 6 and spin-transfer-torque ͑STT͒ switching. 7 In any process involving magnetization dynamics, the Gilbert damping constant ␣ is one key indicator to optimize writing speeds and reduce power consumption.…”

Terahertz magnetic field induced coherent spin precession in YFeO3

“…Magnetization switching and spin precession in magnetically ordered materials under optical pulses have been investigated extensively in the past decade. [1][2][3][4][5] On application of visible or near infrared femtosecond pulses to a magnetic structure, a transient magnetic field is generated through the inverse Faraday effect, 6,7 by which non-thermal magnetization control can be realized with optical pulses. 8,9 Coherent manipulation of spin precession with ultra-fast laser pulses have been studied extensively in a variety of materials, from ferromagnetic dielectric, 1,2 and ferromagnetic metal alloys 4,10 to paramagnetic dielectrics 11 and magnetic ionic liquids.…”

Dynamic and static properties of rigidly fixed ultrathin ferromagnetic films with S = 1 and competing anisotropies

“…(9)- (14) were obtained for J 0 > b xz ; with arbitrary values of the anisotropy constants. Equation (9) implies that when the material constants 1. The system geometry.…”

“…[8][9][10] Thus, for example, nanogranular films with an "easy-axis" anisotropy are of great scientific and practical interest [11][12][13][14] as media with a high information storage density.…”