The 239th Special CMSM seminar

The following three talks will be given.
 

Title: Low Switching Current Spin-Transfer-Torque MRAM

Speaker: Dr. Daniel Worledge, Distinguished Research Staff Member, Senior Manager, MRAM & PCM, IBM Almaden Research Center
 

Abstract:

Spin-Transfer-Torque Magnetic Random Access Memory (MRAM) possesses a unique combination of high speed, high endurance, non-volatility, and small cell size. Write current largely determines the cost of Spin Torque MRAM, since the transistor and hence cell area must be sized large enough to source the write current. This talk will give a brief overview of Spin Torque MRAM, including potential applications and materials challenges. I will then review the discovery of interface perpendicular anisotropy in the Ta|CoFeB|MgO system at IBM and the subsequent perpendicular magnetic tunnel junctions which were developed using it, including demonstration of reliable, high speed spin-torque writing, and results on scaling down to 20 nm. Then I will discuss our recent results on methods to lower the switching current of Spin-Transfer-Torque MRAM by using optimized magnetic materials and double magnetic tunnel junctions.

Title: Field Free Perpendicular Magnetization Switching by Spin Hall Current: Experiments and Modeling

Speaker: Prof. Jimmy Zhu, ABB Professor of Engineering, Carnegie Mellon University

 

Abstract:

Magnetization switching via spin Hall effect which arising from spin orbital torque (SOT) represents as a competitive alternative to that by spin-transfer torque (STT) used for magnetoresistive random access memory (MRAM), as it does not require high-density current to go through the tunnel junction. For perpendicular MRAM, however, SOT driven switching of the free layer requires an external in-plane field, which poses limitation for viability in practical applications. Here we demonstrate field-free magnetization switching of a perpendicular magnet by utilizing an Iridium (Ir) layer. The Ir layer not only provides SOTs via spin Hall effect, but also induce interlayer exchange coupling with an in-plane magnetic layer that eliminates the need for the external field. Such dual functions of the Ir layer allows future build-up of magnetoresistive stacks for memory and logic applications. Experimental observations show that the SOT driven field-free magnetization reversal is characterized as domain nucleation and expansion. Micromagnetic modeling is carried out to provide in-depth understanding of the perpendicular magnetization reversal process in the presence of an in-plane exchange coupling field.

Title: Heat Assisted Magnetic Recording’s Extensibility to High Linear and Areal Density

Speaker: Dr. Jan-Ulrich Thiele, Seagate Technology, Fremont Research Center

 

Abstract:

Heat assisted magnetic recording, or HAMR, is being developed as the next generation magnetic recording technology. Critical components of this technology, such as the plasmonic near field transducer and high anisotropy granular FePt media, as well as recording demonstrations and fully integrated drives have been reported. One of the remaining ongoing challenges of magnetic recording in general and HAMR in particular has been the demonstration of high linear density recording approaching the grain-size limit of the recording media, and a clear pathway to smaller grain sizes while maintaining good magnetic properties and distributions. This paper will demonstrate the extensibility of FePt-based media down to the 5nm center-to-center range. Using recording media with a slightly larger grain size of 7nm center-to-center, in combination with a HAMR head with high thermal gradient >10K/nm, a linear recording density of 3000 kbpi, or a bit length of 8.5nm, approaching the grain size limit of this media, has been demonstrated.