Magnetization dynamics of irradiation-fabricated perpendicularly magnetized dots inside a softer magnetic matrix

AbstractGlobal Helium ion irradiation can tune the magnetic properties of thin films, notably their magneto-crystalline anisotropy. Helium ion irradiation through nanofabricated masks can been used to produce sub-micron planar magnetic nanostructures of various types. Among these, perpendicularly magnetized dots in a matrix of weaker magnetic anisotropy are of special interest because their quasi-static magnetization reversal is nucleation-free and proceeds by a very specific domain wall injection from the magnetically “soft” matrix, which acts as a domain wall reservoir for the “hard” dot. This guarantees a remarkably weak coercivity dispersion. This new type of irradiation-fabricated magnetic device can also be designed to achieve high magnetic switching speeds, typically below 100 ps at a moderate applied field cost. The speed is obtained through the use of a very high effective magnetic field, and high resulting precession frequencies. During magnetization reversal, the effective field incorporates a significant exchange field, storing energy in the form of a domain wall surrounding a high magnetic anisotropy nanostructure's region of interest. The exchange field accelerates the reversal and lowers the cost in reversal field. Promising applications to magnetic storage are anticipated.

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Size Influence on Magnetic Properties of Nickel Hollow Spheres

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.321 ◽

2013 ◽

Vol 652-654 ◽

pp. 321-326

Author(s):

Zhi Bin Li ◽

Rui Rong Wang ◽

Yi Da Deng

Keyword(s):

Heat Treatment ◽

Grain Size ◽

Magnetic Properties ◽

Domain Wall ◽

Magnetic Anisotropy ◽

Magnetization Reversal ◽

Treatment Process ◽

Reduction Method ◽

Hollow Spheres ◽

Heat Treatment Process

Nickel hollow spheres (NHSs) with different diameter have been synthesized by the autocatalytic reduction method. The morphology, size distribution and magnetic properties of NHSs were characterized. The results indicate that when the nickel hollow spheres become smaller, mechanism of magnetization reversal varies from motion of domain wall to spin coherent rotation. After the heat treatment process, the grain size of samples becomes bigger and coercivity is enhanced because domain wall is pinned by local magnetic anisotropy induced spontaneously.

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On the local magnetization reversal in front of a domain wall moving in a garnet ferrite film with orthorhombic magnetic anisotropy

Physics of the Solid State ◽

10.1134/1.1626748 ◽

2003 ◽

Vol 45 (11) ◽

pp. 2124-2127

Author(s):

V. V. Randoshkin

Keyword(s):

Domain Wall ◽

Magnetic Anisotropy ◽

Magnetization Reversal ◽

Ferrite Film ◽

Local Magnetization ◽

Garnet Ferrite

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Precessional strategies for the ultrafast switching of soft and hard magnetic nanostructures

MRS Proceedings ◽

10.1557/proc-746-q8.4 ◽

2002 ◽

Vol 746 ◽

Cited By ~ 1

Author(s):

T. Devolder ◽

M. Belmeguenai ◽

H. W. Schumacher ◽

C. Chappert ◽

Y. Suzuki

Keyword(s):

Domain Wall ◽

Early Stage ◽

Spin Valve ◽

Magnetic Nanostructures ◽

Transverse Field ◽

Anisotropy Field ◽

Cost Effective ◽

Magnetic Storage ◽

Easy Magnetization ◽

Wall Width

ABSTRACTWe discuss the precessional, quasi-ballistic switching of magnetization in magnetic nanostructures. In soft spin-valve cells, fast and energy-cost effective magnetization switching can be triggered by a transverse field pulse of moderate amplitude, below the in plane anisotropy field, because of an amplification effect brought by the demagnetizing field at the early stage of the reversal. The same effect is no more possible in hard nanomagnets with perpendicular easy magnetization axis. We propose a new type of nanostructured magnetic device, designed to overcome this limitation. The speed is obtained through the use of a very high effective magnetic field, obtained by incorporating a significant exchange field which stores the energy in the form of a constrained domain wall surrounding a region of high magnetic anisotropy. This stored energy is partially available to accelerate the magnetization reversal in a precessional scenario. We illustrate the concept by studying numerically a model system. The key parameter for the reversal is the ratio of the domain wall width to the structure lateral dimension. Possible routes for device preparation are discussed. Promising application to magnetic storage are anticipated.

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Effects of ion irradiation on epitaxial Cu/Ni/Cu(001) with perpendicular magnetic anisotropy

Applied Physics Letters ◽

10.1063/1.1515877 ◽

2002 ◽

Vol 81 (21) ◽

pp. 4017-4019 ◽

Cited By ~ 12

Author(s):

T. G. Kim ◽

Y. H. Shin ◽

J. H. Song ◽

M. C. Sung ◽

I. S. Kim ◽

...

Keyword(s):

Magnetic Anisotropy ◽

Ion Irradiation ◽

Perpendicular Magnetic Anisotropy

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Subsystem domination influence on magnetization reversal in designed magnetic patterns in ferrimagnetic Tb/Co multilayers

Scientific Reports ◽

10.1038/s41598-020-80004-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Łukasz Frąckowiak ◽

Feliks Stobiecki ◽

Gabriel David Chaves-O’Flynn ◽

Maciej Urbaniak ◽

Marek Schmidt ◽

...

Keyword(s):

Domain Wall ◽

Magnetization Reversal ◽

Domain Walls ◽

Compensation Point ◽

Relative Sign ◽

Reversal Process ◽

Effective Magnetization ◽

Domain Wall Propagation ◽

Characteristic Features ◽

Magnetization Reversal Process

AbstractRecent results showed that the ferrimagnetic compensation point and other characteristic features of Tb/Co ferrimagnetic multilayers can be tailored by He+ ion bombardment. With appropriate choices of the He+ ion dose, we prepared two types of lattices composed of squares with either Tb or Co domination. The magnetization reversal of the first lattice is similar to that seen in ferromagnetic heterostructures consisting of areas with different switching fields. However, in the second lattice, the creation of domains without accompanying domain walls is possible. These domain patterns are particularly stable because they simultaneously lower the demagnetizing energy and the energy associated with the presence of domain walls (exchange and anisotropy). For both lattices, studies of magnetization reversal show that this process takes place by the propagation of the domain walls. If they are not present at the onset, the reversal starts from the nucleation of reversed domains and it is followed by domain wall propagation. The magnetization reversal process does not depend significantly on the relative sign of the effective magnetization in areas separated by domain walls.

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