APPLICATIONS OF TECHNOLOGY:
- Magnetic data storage media
- Magnetic read head
- Thermally assisted magnetic recording
ADVANTAGES:
- Overcomes superparamagnetic limit for magnetic media
- Reduces energy consumption for hard disk storage systems
- Perpendicular alignment and control of FM / AFM layers
- Applicable to read-head design
ABSTRACT:
A Berkeley Lab team led by Frances Hellman has developed a technology to improve the stability and capacity of perpendicular magnetic media and decrease the energy consumption required to write magnetic information. The researchers found an antiferromagnetic (AFM) material which, when grown under certain conditions, has preferential magnetic orientation perpendicular to the plane, like the ferromagnetic (FM) material used to store the information, which improves the magnetic stability of small, perpendicularly written magnetic domains.
The Berkeley Lab innovation is a promising advance particularly for an emerging technology known as thermally assisted magnetic recording (TAMR), which was developed as a strategy to sidestep both the superparamagnetic limit of longitudinal storage media and the high switching field required to write magnetic information in the storage layer. One form of TAMR takes advantage of a phase change in iron-rhodium (FeRh) that causes it, at about 90°C, to switch from an AFM state, to a FM state. At this elevated temperature, data therefore can be more easily written onto the adjacent exchange-coupled FM storage medium layer (typically FePt) because of exchange spring coupling with the FM FeRh layer. But when these written domains are cooled to room temperature, the FeRh is again an AFM, and data bits are stabilized by the high coercivity of the FePt storage layer. The orientation of the FeRh magnetic moments is planar so far.
The Berkeley Lab technology improves the magnetic coupling between these two layers by forcing the FeRh magnetic moments to point perpendicular to the plane. Under specific growth conditions, this preferred orientation can be obtained in both magnetic phases of FeRh. Then the interfacial AFM (FeRh) / FM (storage medium, e.g. FePt) coupling along the normal to the film plane provides an enhanced writability (lower switching field) at high temperature and enhanced stability at room temperature, allowing for a reduced domain size and therefore an increased storage capacity. Another field of application of these perpendicularly oriented FeRh films in the AFM phase would be as a pinning layer in a spin-valve stack of perpendicularly magnetized FM layers for an improved read-out resolution.
Data storage technology is rapidly approaching a fundamental limit on the size that a bit of data (0 or 1) can occupy on a magnetic media surface. At a sufficiently small scale, superparamagnetic effects cause ferromagnetic (FM) nanograins to switch their magnetization direction spontaneously, thereby erasing stored data. In current longitudinal recording technology, an AFM adjacent layer is commonly used to stabilize the magnetic information stored in the active FM layer. With the advent of perpendicular FM active layers, it is desirable that this AFM adjacent layer also have magnetic orientation perpendicular to the plane, but current AFM materials have in plane magnetic orientation. The Berkeley Lab technology overcomes this limitation.
DEVELOPMENT STAGE: Early stage research
STATUS: Patent pending. Available for licensing or collaborative research.
FOR MORE INFORMATION:
SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:
Nanoparticles for Ultrahigh Density, Non-Volatile Information Storage, IB-2399
REFERENCE NUMBER: JIB-3215
