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Toshiba Develops the World’s First Analysis Method for Determining the Oscillation State of Spin-Torque Oscillators for MAS-MAMR

-Contributing to the development of next-generation large-capacity nearline hard disks-

22 Jan, 2026
Toshiba Corporation

Overview

KAWASAKI - Toshiba has developed the world’s first method for determining in detail the oscillation state of the spin-torque oscillators (STOs) in the recording head for microwave-assisted switching-microwave-assisted magnetic recording (MAS-MAMR), which is a next-generation technology with the potential to realize even larger capacity hard disk drives (HDDs).
HDDs that can store massive amounts of data at low cost are still important as storage devices, and there is demand for even higher recording density. Toshiba is developing both MAS-MAMR and heat-assisted magnetic recording (HAMR) as next-generation recording technologies, and has demonstrated world-leading improvements in recording performance in MAS-MAMR in particular through the company’s unique bi-oscillation type STO (dual-FGL STO)*1.
The STO oscillation state necessary for obtaining optimal microwaves needs to be accurately determined and applied to the design in order to make MAS-MAMR practical. However, this has conventionally been difficult to analyze in detail.
Toshiba has developed an innovative method of directly evaluating the oscillation state of an STO through collaborative research with the National Institute for Materials Science (NIMS) of Japan. This method will deepen the understanding of STO operation, including dual-FGL STOs, and will contribute to the advancement of MAS-MAMR technology. Toshiba is working on developing both MAS-MAMR and HAMR technologies to promote the development of next-generation nearline HDDs.
This research result was published on January 21, 2026 in Communications Physics, a scientific journal in the field of physics published by Nature Portfolio that reports on topics such as new experimental results*2, new technologies, and computational methods that have an impact on research in various fields of physics.

Development background

Life has been greatly changed by the expanding digitalization of society and the rapid advancement of generative AI. The need for information storage is ever-increasing, with the shipped capacity of HDDs exceeding 1 ZB (= 1 billion terabytes) in 2024. HDDs still play a central role in information storage. The HDD market is expected to reach 32 billion USD by 2030, and the large capacity nearline HDD market for data centers is expected to grow in particular*3. Against this background, there is strong demand for ever larger capacities in the future.
The key to realizing this increase in capacity is energy-assisted magnetic recording technology, which is a new recording method. Toshiba has been working on the development of two energy-assisted magnetic recording technologies: MAS-MAMR, in which the magnetic recording medium is irradiated with microwaves; and HAMR in which heat is applied.
The microwave source in MAS-MAMR is an STO at the tip of the recording head. Toshiba has proven itself to be a world leader by proposing and designing its own unique dual-FGL STO and improving recording performance with MAS-MAMR*1. In the dual-FGL STO, the microwaves optimized for MAS-MAMR are generated by the coordinated oscillation of two internal magnetic layers. The stability, frequency, intensity, and oscillation direction of microwaves are important factors for increasing the recording density of MAS-MAMR, and analyzing and understanding the oscillation state of the STO that is the source of these microwaves is essential for improving STO designs and increasing the capacity of HDDs even further.
However, recording heads have a complicated structure, and directly observing the nanoscale STO that is mounted there to analyze the oscillation state has proved extremely difficult. Although oscillation states have conventionally been inferred through a combination of multiple pieces of indirect data such as simulation results and recording properties, gaining an understanding through direct measurement has become a key to developing more advanced technology.

Features of the technology

Toshiba has developed the world’s first analysis method that can determine in detail the STO oscillation state through collaborative research with NIMS. This method has enabled direct observation of the oscillation state, which has conventionally been difficult to do, by newly introducing an antenna for evaluation and using it to illuminate the STO with external microwaves (Figure 1).
This method focuses on a synchronization phenomenon between the STO oscillation and the microwaves emitted from the evaluation antenna. The presence of the synchronization phenomenon varies depending on the oscillation state of the STO. In particular, this phenomenon does not appear in the bi-oscillation state that is the aim of a dual-FGL STO. Even in cases where the oscillation signals cannot be distinguished by conventional measurement, this new method clearly distinguishes between the bi-oscillation state and non-bi-oscillation state, enabling clear determination of the oscillation state (Figure 2). Although there may be multiple oscillation signals depending on the STO oscillation state, these can be measured at the frequency level, meaning that the true frequency of the best oscillation state for MAS-MAMR can be identified.
Although the recording head has a complicated structure, only the STO responds sharply to the microwaves from the evaluation antenna, so this makes the measurements specific to the STO. Although complicated wiring was conventionally needed for accurate evaluation, with this new method, the evaluation can be completed simply by introducing an antenna. This is the world’s first method that can directly identify within the recording head the state of an STO oscillating at high frequencies of several tens of gigahertz.
Furthermore, STOs are expected to find applications in next-generation computing systems such as neuromorphic computing, which is a computing method that emulates the function of the human brain, and reservoir computing which is suitable for time-series data processing. This new method is broadly applicable to various kinds of STOs.

Figure 1: Schematic diagrams of a MAS-MAMR recording operation and this analysis method
Figure 2: Distinguishing between oscillation states of a dual-FGL STO by this evaluation method

Future developments

This method is expected to contribute to progress in understanding the behavior of STOs, thereby improving and advancing the design of STOs, and promoting MAS-MAMR technology. Toshiba is continuing to accelerate the development of next-generation HDDs using both MAS-MAMR technology and HAMR technology, and to provide solutions in response to a diverse range of storage needs such as those for the rapidly growing data centers and generative AI.