Posted on

Magnetic-permeability technology may radically lower disk-drive storage limits

Scanning electron microscope image of 300-nm-diameter bits created in magnetic-permeability-based storage material (credit: John Timmerwilke et al./Journal of Physics D)

A new magnetic-memory technology that is far less susceptible to corruption by magnetic fields, thermal exposure, or radiation effects than conventional ferromagnetic memory has been developed by a research team led by U.S. Army Research Laboratory physicist Alan Edelstein, PhD.

(Ferromagnetic materials are used to store data in hard drives and magnetic-stripe credit cards.)

The idea is to avoid corruption of data stored magnetically from heating (which limits the data density of hard drives) or random magnetic fields (which can erase data on credit cards and other cards using a magnetic stripe).

The technique uses thermal heating with a laser to crystallize ferromagnetic materials in a pattern corresponding to the binary data to be stored (a 1 could be represented by a crystallized area and a zero by a non-crystallized area, for example). The crystalline areas have lower magnetic “permeability” (how easily a material is affected by a magnetic field), so information can later be read from the memory by using a probe containing a magnetic field without erasing or overwriting data.

Solving magnetic-stripe and disk-drive limitations

This new magnetic-permeability-based approach is an improvement over conventional magnetic data storage in the magnetic strip of a credit card, in which data is written using a magnetic field. That means it can also be erased by a magnetic field — which is why credit cards or hotel room cards sometimes fail. (RFID chips have been developed to fix that problem, but these can be read by a passer-by using an RFID reader so they may not be secure.)

The new approach also overcomes the “superparamagnetic limit” to how small the particles used in disk-drive memory can be. With the magnetic-permeability approach, the limiting factors (which are lower) are microstructure and composition of the material.

With the new approach, memory is also less prone to degradation when exposed to gamma radiation. That’s important for space travel because it eliminates the need for shielding and thus reduces weight.

“At present we have low-density-sized bits,” said Edelstein. “But we have the potential to get much higher since we are not limited by the superparamagnetic limit. There are difficult technological limitations to overcome first though. We’ve [also] demonstrated the ability to rewrite bits for a read/write memory, and hope to publish the results soon,” he said.

The research was published today (Friday Sept. 11) in the Journal of Physics D: Applied Physics. Other authors are researchers at Corning Incorporated, Naval Research Laboratory, and University of Nebraska, Lincoln.

Abstract of Using magnetic permeability bits to store information

Steps are described in the development of a new magnetic memory technology, based on states with different magnetic permeability, with the capability to reliably store large amounts of information in a high-density form for decades. The advantages of using the permeability to store information include an insensitivity to accidental exposure to magnetic fields or temperature changes, both of which are known to corrupt memory approaches that rely on remanent magnetization. The high permeability media investigated consists of either films of Metglas 2826 MB (Fe40Ni38Mo4B18) or bilayers of permalloy (Ni78Fe22)/Cu. Regions of films of the high permeability media were converted thermally to low permeability regions by laser or ohmic heating. The permeability of the bits was read by detecting changes of an external 32 Oe probe field using a magnetic tunnel junction 10 μm away from the media. Metglas bits were written with 100 μs laser pulses and arrays of 300 nm diameter bits were read. The high and low permeability bits written using bilayers of permalloy/Cu are not affected by 10 Mrad(Si) of gamma radiation from a 60Co source. An economical route for writing and reading bits as small at 20 nm using a variation of heat assisted magnetic recording is discussed.

Posted on

Discovery of Homo naledi adds a new branch to the human family tree

Skeletal fossil of the hand of Homo naledi (photo credit: John Hawks, UW–Madison)

An international research team has discovered a new species of a human relative, Homo naledi, uncovered in a cave outside of Johannesburg, South Africa. The discovery in late 2013 may shed light on the diversity of our genus and possibly its origin.

The team’s findings, which are published in two papers in the open-access journal eLife, were announced by South Africa’s University of the Witwatersrand, the National Geographic Society, and the South African National Research Foundation.

Homo naledi: A New Species on the Human Family Tree (illustration credit: S.V. Medaris/UW-Madison)

The authors describe Homo naledi as being similar in size and weight to a small modern human, with human-like hands and feet. The skull had a small braincase “similar in size to other early hominin species that lived between four million and two million years ago.”

The discovery indicates that H. naledi intentionally deposited bodies of its dead in a remote cave chamber — behaviors previously thought limited to humans.

This figure includes the 737 partial or complete anatomical elements of Homo naledi found (credit: Lee R. Berger et al./eLife)

Lee Berger, a research professor in the Evolutionary Studies Institute at the University of the Witwatersrand and a National Geographic Explorer-in-Residence, led the expeditions that recovered the fossils — more than 1,500 bones belonging to at least 15 individuals.

The National Geographic article “This Face Changes the Human Story. But How?” offers striking art and photography on this discovery.


University of Wisconsin-Madison | Meet our newest ancestor: Homo naledi

Abstract of Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa
Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis orHomo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

Abstract of Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa

We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.