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Spin-Polarized Tunneling Storage Device

IP.com Disclosure Number: IPCOM000040129D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Reihl, B: AUTHOR

Abstract

Increasing demand for storage devices with higher packing densities requires the use of smaller domain structures than employed in the Winchester and bubble-domain-type memories. A lateral resolution in the 0.1 nanometer range permitting to obtain information on the magnetic domains as well as on the domain walls, i.e., on the changes of magnetization in real space, is achieved with a technique which benefits from the characteristics of the scanning tunneling micorscope (STM). Two tunneling tips, one operated in the conventional STM mode and the other in the spin polarized mode, are scanned in parallel across the record medium. The conventional tip is regulated via feedback on a constant tunneling current.

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Spin-Polarized Tunneling Storage Device

Increasing demand for storage devices with higher packing densities requires the use of smaller domain structures than employed in the Winchester and bubble-domain-type memories. A lateral resolution in the 0.1 nanometer range permitting to obtain information on the magnetic domains as well as on the domain walls, i.e., on the changes of magnetization in real space, is achieved with a technique which benefits from the characteristics of the scanning tunneling micorscope (STM). Two tunneling tips, one operated in the conventional STM mode and the other in the spin polarized mode, are scanned in parallel across the record medium. The conventional tip is regulated via feedback on a constant tunneling current. It pulls behind it the second tip of which the spin polarized tunneling current is monitored as a function of the xy-scanning of the first tip. Positive (negative) current changes correspond to magnetic domains with parallel (antiparallel) magnetization directions. The spin polarization at the second tip is obtained through the use of a ferromagnetic semiconductor, such as EuS, for example, coated onto a tungsten tip. Below its Curie temperature, a heterojunction tip of this type acts as an almost perfect spinfilter for electrons tunneling from the tungsten Fermi level via the EuS conduction band into vacuum. An alternative material EuS would be EuO. If a <112> tungsten tip is used, a transversly polarized tunneling curre...