Direct Real‐Space Observation of Stochastic Behavior in Domain Nucleation Process on a Nanoscale

Abstract

Stochastic behavior of nucleationprocess during magnetization reversalon a nanoscale in a nanogranularCoCrPt alloy film is directly observedutilizing magnetic soft X‐raytransmission microscopy, whichprovides a spatial resolution of 15 nm.Thermal fluctuations in the orientationof the magnetic moments of the grainsplay a dominant role for the stochasticnature of domain nucleation in this system.

Oscillating spatial dependence of domain memory in ferromagnetic films mapped via x-ray speckle correlation

“…Now, by mapping ρ (Q,H,T), we probe MDM in further dimensions, revealing its dependence with spatial scales. The correlation technique used here quantifies MDM as function of Q -the wave vector in scattering space-and thus provides a unique information, complementary to direct imaging techniques like X-ray microscopy (XRM) [19], Kerr microscopy [20], photoelectron emission microscopy (PEEM) [21], where the structure and magnetic configuration of a film is generally sampled over smaller local area with less statistical information in terms of correlation lengths, or like MFM [22], providing only a superficial view of the magnetic configuration via magnetic stray fields.…”

Stochastic formation of magnetic vortex structures in asymmetric disks triggered by chaotic dynamics

“…From those measurements, the transition of dominantly created circularity from c ¼ À 1 to c ¼ þ 1 with increasing the interdisk distance is also evident. The experimentally observed phenomena, particularly the V-shaped dependency of stochasticity on the interdisk distance is very intriguing as it cannot originate from thermal fluctuation effect, which has been considered as the main cause of stochastic behaviour in magnetic processes [9][10][11] . Thermal fluctuations should not depend on the interdisk distance because the thermal fluctuations (Bk B TV À 1 ) (refs 35,36) are mainly determined by the temperature T and the island volume V, the unit volume relevant to thermal stability and not by geometrical parameters, such as the interdisk distance.…”

“…As the length scales in nanomagnetism approach fundamental limits such as the exchange lengths, the question arises, whether there is an intrinsic stochastic nature, which ultimately would tremendously affect the performance of high-density magnetic storage devices aiming at faster processing speed. Understanding and controlling stochastic behaviour in nanoscale magnetic systems are thus a topic of paramount interest and numerous studies have been performed, for example, on magnetization reversal of nano-size domains in ultrathin magnetic films 5,8,9 and domain wall motion in magnetic nanowires 7,10,11 .…”

Microscopic reversal magnetization mechanisms in CoCrPt thin films with perpendicular magnetic anisotropy: Fractal structure versus labyrinth stripe domains

“…This was obtained using the first-order reversal curves (FORC) technique in combination with transmission x-ray microscopy and resonant x-ray small-angle scattering. Im et al [24,25] studied the nucleation process via individual Barkhausen avalanches in 50-nm-thick (Co 0.83 Cr 17 ) 87 Pt 13 alloy films through magnetic soft x-ray transmission microscopy. Schwarz et al [26] examined the mechanisms of the reversal processes by the detection of individual Barkhausen jumps on the nanometer scale in granular La 0.7 Sr 0.3 MnO 3 thin films using ultrahighvacuum low-temperature magnetic force microscopy (MFM).…”