Picosecond time-resolved magnetization dynamics of thin-film heads

Applied Physics Letters

et al. 2013

mentioning

confidence: 99%

Time resolved scanning Kerr microscopy of hard disk writer structures with a multilayered yoke

Gangmei

Applied Physics Letters

et al. 2013

“…The high spatio-temporal resolution of TRSKM makes it a powerful tool with which to study the magnetization dynamics of individual sub-micron ferromagnetic elements. One of the first applications was to image the switching of the pole pieces of a recording head [34]. A vector-resolved version of TRSKM, capable of measuring three orthogonal components of the magnetization vector, allowed the trajectory of the magnetization precession to be determined [36,37], and led to the demonstration of precessional switching of a micrometre-sized magnetic element [38,39].…”

Section: Dynamical Phenomena and Measurement Techniquesmentioning

confidence: 99%

“…The spatial resolution of TR-MOKE experiments can be significantly enhanced by using a scanning microscope. In time-resolved scanning Kerr microscopy (TRSKM) [33], magnetic samples are integrated with a microscale planar waveguide so that a pulsed [34] or harmonic magnetic field [35] may be used to excite magnetization dynamics. The high spatio-temporal resolution of TRSKM makes it a powerful tool with which to study the magnetization dynamics of individual sub-micron ferromagnetic elements.…”

Section: Dynamical Phenomena and Measurement Techniquesmentioning

confidence: 99%

Ultrafast magnetization dynamics of spintronic nanostructures

Phil. Trans. R. Soc. A.

Kruglyak

Gangmei

et al. 2011

The ultrafast (sub-nanosecond) magnetization dynamics of ferromagnetic thin films and elements that find application in spintronic devices is reviewed. The major advances in the understanding of magnetization dynamics in the two decades since the discovery of giant magnetoresistance and the prediction of spin-transfer torque are discussed, along with the plethora of new experimental techniques developed to make measurements on shorter length and time scales. Particular consideration is given to time-resolved measurements of the magneto-optical Kerr effect, and it is shown how a succession of studies performed with this technique has led to an improved understanding of the dynamics of nanoscale magnets. The dynamics can be surprisingly rich and complicated, with the latest studies of individual nanoscale elements showing that the dependence of the resonant mode spectrum upon the physical structure is still not well understood. Finally, the article surveys the prospects for development of high-frequency spintronic devices and highlights areas in which further study of fundamental properties will be required within the coming decade.

“…Increased data rates in perpendicular magnetic recording 1 (PMR) require the magnetization within the recording head to respond to the driving field sufficiently quickly that erase after write 2 (EAW) phenomena are avoided. Previous studies [3][4][5][6][7][8][9] have addressed the rise time and remnant value of the write field at the pole tip. However, magnetic flux 10 is delivered to the confluence and tip regions from the yoke by a process known as "flux beaming."…”

mentioning

confidence: 99%

Time resolved imaging of magnetization dynamics in hard disk writer yokes excited by bipolar current pulses

Journal of Applied Physics

Hicken

et al. 2014

A partially built hard disk writer structure with a NiFe/CoFe/Ru/NiFe/CoFe synthetic antiferromagnetic (SAF) yoke was studied by time and vector resolved scanning Kerr microscopy. All three time dependent components of the magnetization were recorded simultaneously as a bipolar current pulse with 1 MHz repetition rate was delivered to the coil. The component of magnetization parallel to the symmetry axis of the yoke was compared at the pole and above a coil winding in the centre of the yoke. The two responses are in phase as the pulse rises, but the pole piece lags the yoke as the pulse falls. The Kerr signal is smaller within the yoke than within the confluence region during pulse cycling. This suggests funneling of flux into the confluence region. Dynamic images acquired at different time delays showed that the relaxation is faster in the centre of the yoke than in the confluence region, perhaps due to the different magnetic anisotropy in these regions. Although the SAF yoke is designed to support a single domain to aid flux conduction, no obvious flux beaming was observed, suggesting the presence of a more complicated domain structure. The SAF yoke writer hence provides relatively poor flux conduction but good control of rise time compared to single layer and multi-layered yokes studied previously.