Semiconductor Research Corporation and University of California, Davis Explore New Materials and Device Structures

University of California, Davis‘ researchers sponsored by Semiconductor Research Corporation (SRC), an university-research consortium for semiconductors and related technologies, are exploring new materials and device structures to develop next-generation memory technologies.

The team assigned red (magnetization pointing right) to be “1” and blue (magnetization pointing left) to be “0”; four notches along a one-dimensional nanowire with only one domain wall are in white. In Panel (b) (shown on left), the data before the domain wall are “1”s and the data after the domain wall are “0”s, as indicated that in the detail view of Panel (b) (right side). Panel c shows a different shaped domain wall.
(Source: UC Davis)

The research promises to help storage companies advance their technologies with predicted benefits including increased speed, lower costs, higher capacity, more reliability and improved energy efficiency compared to today’s HDD and RAM solutions.

Conducted by UC Davis’ Takamura Research Group that has experience in the growth and characterization of complex oxide thin films, heterostructures and nanostructures, the research involves leveraging complex oxides to manipulate magnetic domain walls within the wires of semiconductor memory devices at nanoscale dimensions. This work utilized sophisticated facilities available through the network of Department of Energy-funded national laboratories at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory and the Advanced Light Source, Lawrence Berkeley National Laboratory.

Existing HDD and RAM solutions store data either based on the magnetic or electronic state of the storage medium. HDD drives provide a lower cost solution for ultra-dense storage, but are relatively slow and suffer reliability issues due to the movement of mechanical parts. Solid state solutions, such as flash memory for long-term storage,d DRAM for short-term storage, offer higher access speeds, but can store fewer bits per unit area and are more costly per bit of data stored.

An alternative technology that may address both of these shortcomings is based on the manipulation of magnetic domain walls, regions that separate two magnetic regions. This technology, originally proposed by IBM Corp.‘s researchers and named Race Track Memory, is where the UC Davis work picked up.

With most previous studies focused on metallic magnetic materials and their alloys du to well-established processing steps and high Curie temperatures, challenges still remain in manipulating parameters such as the type of domain walls formed, their position within the nanowires and their controlled movement along the length of the nanowires.

The UC Davis research investigates the use of complex oxides, such as La0.67Sr0.33MnO3 (LSMO), and heterostructures with other complex oxides as candidate materials. Complex oxides are part of an exciting new class of so-called ‘multifunctional’ materials that exhibit multiple properties (e.g. electronic, magnetic, etc.) and may thereby enable multiple functions in a single device. For the case of LSMO, it is a half metal, exhibits colossal magnetoresistance (CMR), meaning it can dramatically change electrical resistance in the presence of a magnetic field, and undergoes a simultaneous ferromagnetic-to-paramagnetic and metal-to-insulator transition at its Curie temperature.

In addition, these properties are sensitive to external stimuli, such as applied magnetic/electric fields, light irradiation, pressure and temperature. These attributes may allow researchers to better manipulate the position and movement of the magnetic domain walls along the length of the nanowires.

“While still in the early stages, the innovative research from the UC Davis team is helping the industry gain a better fundamental understanding linking the chemical, structural, magnetic and electronic properties of next-generation memory materials,” said Bob Havemann, director of nanomanufacturing sciences, SRC.