Layer-resolved readout of magnetic signals using ferromagnetic resonance effect

Yang, Tao; Suto, Hirofumi; Nagasawa, Tooru; Kudo, Kiwamu; Mizushima, Koichi; Sato, Rie

doi:10.1016/j.jmmm.2012.12.004

Cited by 6 publications

(3 citation statements)

References 18 publications

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“…Ferromagnetic resonance (FMR) has long been studied as a subject of fundamental physics as well as a tool for observing the magnetic states of materials and devices. Recently, the use of FMR has been proposed for three-dimensional (3D) (or multilayer) recording to increase recording density in hard disk drives (HDDs) [1][2][3][4][5][6][7][8][9][10]. The use of FMR enables layer-selective writing [1][2][3][4][5][6][7] and reading [1,2] by employing recording layers (RLs) with different FMR frequencies and then selectively inducing FMR by using a microwave field of the corresponding frequency.…”

Section: Introductionmentioning

confidence: 99%

Layer-selective detection of magnetization directions from two layers of antiferromagnetically-coupled magnetizations by ferromagnetic resonance using a spin-torque oscillator

Kanao

Suto

Mizushima

et al. 2020

Journal of Magnetism and Magnetic Materials

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A B S T R A C TWe use micromagnetic simulation to demonstrate layer-selective detection of magnetization directions from magnetic dots having two recording layers by using a spin-torque oscillator (STO) as a read device. This method is based on ferromagnetic resonance (FMR) excitation of recording-layer magnetizations by the microwave field from the STO. The FMR excitation affects the oscillation of the STO, which is utilized to sense the magnetization states in a recording layer. The recording layers are designed to have different FMR frequencies so that the FMR excitation is selectively induced by tuning the oscillation frequency of the STO. Since all magnetic layers interact with each other through dipolar fields, unnecessary interlayer interferences can occur, which are suppressed by designing magnetic properties of the layers. We move the STO over the magnetic dots, which models a read head moving over recording media, and show that changes in the STO oscillation occur on the one-nanosecond timescale.

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Section: Introductionmentioning

confidence: 99%

Layer-selective detection of magnetization directions from two layers of antiferromagnetically-coupled magnetizations by ferromagnetic resonance using a spin-torque oscillator

Kanao

Suto

Mizushima

et al. 2020

Journal of Magnetism and Magnetic Materials

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“…This is because the conventional readout method based on the detection of stray fields senses the superposition of stray fields from the data bits in all recording layers, and thus it cannot selectively read the data stored in a specific recording layer. In an attempt to solve this problem, we recently reported studies on ferromagnetic resonance (FMR) excitation of magnetic multilayer films through using a vector network analyzer (VNA) [16,17]. By providing each recording layer with a different FMR frequency, microwave signal matching to one of these frequencies can excite FMR in a specific recording layer; subsequently, detecting the absorption of microwave signals by FMR excitation can selectively reveal the magnetization direction of the layer.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale layer-selective readout of magnetization direction from a magnetic multilayer using a spin-torque oscillator

et al. 2014

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Technology for detecting the magnetization direction of nanoscale magnetic material is crucial for realizing high-density magnetic recording devices. Conventionally, a magnetoresistive device is used that changes its resistivity in accordance with the direction of the stray field from an objective magnet. However, when several magnets are near such a device, the superposition of stray fields from all the magnets acts on the sensor, preventing selective recognition of their individual magnetization directions. Here we introduce a novel readout method for detecting the magnetization direction of a nanoscale magnet by use of a spin-torque oscillator (STO). The principles behind this method are dynamic dipolar coupling between an STO and a nanoscale magnet, and detection of ferromagnetic resonance (FMR) of this coupled system from the STO signal. Because the STO couples with a specific magnet by tuning the STO oscillation frequency to match its FMR frequency, this readout method can selectively determine the magnetization direction of the magnet.

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“…[6][7][8] It is expected that this unique frequency dependence of the MAS behavior is one of the very important features of this technology for designing MAMR systems and also for realizing multilevel magnetic recording by stacking multiple recording layers with different frequency responses. [9][10][11][12][13][14] From a practical point of view, the implementation of MAS using a granular magnetic film is very important for the realization of MAMR. Very recently, some experiments on the MAS in granular films have been reported.…”

mentioning

confidence: 99%

Influence of intergrain interactions and thermal agitation on microwave-assisted magnetization switching behavior of granular magnetic film

Okamoto

Kikuchi

Kitakami

et al. 2017

Appl. Phys. Express

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Microwave-assisted magnetization switching (MAS) in a granular magnetic film is examined by computer simulation. Contrary to the macrospin calculation and the experiments on single magnetic dots reported so far, in which the switching field linearly decreases with increasing rf frequency and then sharply increases at the critical frequency, the granular film exhibits considerably broad MAS behavior against the rf frequency. This broad MAS behavior is mainly caused by the dispersion of magnetic properties and thermal agitation. On the other hand, intergrain dipolar and exchange interactions enhance the MAS effect in the granular film and suppress the MAS broadening.

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Layer-resolved readout of magnetic signals using ferromagnetic resonance effect

Cited by 6 publications

References 18 publications

Layer-selective detection of magnetization directions from two layers of antiferromagnetically-coupled magnetizations by ferromagnetic resonance using a spin-torque oscillator

Layer-selective detection of magnetization directions from two layers of antiferromagnetically-coupled magnetizations by ferromagnetic resonance using a spin-torque oscillator

Nanoscale layer-selective readout of magnetization direction from a magnetic multilayer using a spin-torque oscillator

Influence of intergrain interactions and thermal agitation on microwave-assisted magnetization switching behavior of granular magnetic film

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