Spin valves are essential building blocks in the magnetic sensors of read heads in hard disk drives. They consist of two magnetic layers separated by a non-magnetic layer and act as valves for electrons depending on the relative alignment of the magnetization (spin) in the magnetic layers.
With the continuous push to boost the storage density of disk drives, it has become increasingly important to shield each individual sensor from the magnetic flux of adjacent bits. However, the current approach of placing the read sensor between two magnetic shields limits the resolution with which information can be packed.
To circumvent this issue, a read sensor using a 'differential dual spin valve' (DDSV) was previously proposed by Guchang Han and co-workers at the A*STAR Data Storage Institute. Based on two spin valves separated by a gap layer, it is not influenced by uniform magnetic fields (unlike single spin valve read sensors) but on field gradients. As Han explains, the packing resolution is thereby no longer limited by the magnetic shield-to-shield spacing, but by the thickness of the two active layers in the spin valves (called free layers) and the gap layer separating them.
In a significant step in understanding how the reading performance of DDSVs is affected by further downscaling of the device dimensions, Han and his colleagues have now systematically studied the magnetic interactions between the free layers as a function of their thicknesses as well as the gap layer material and thickness1.
“There are mainly two types of interlayer interactions between the two free layers,” says Han. One is a magnetostatic interaction, which propagates along the edges of the device. The other is mediated through the gap layer by either free electrons (the so-called RKKY interaction) or magnetic poles formed at the rough interfaces between the gap and free layers (Néel coupling).
While the Néel coupling is always ferromagnetic, thus favoring parallel alignment of the magnetizations in the free layers, the RKKY interaction can be either ferro- or antiferromagnetic , depending on the gap layer thickness and material. “From a DDSV working principle, it is desirable to have the two free layers couple antiferromagnetically,” notes Han.
For patterned DDSV samples, the researchers showed that the magnetostatic edge coupling dominates the switching behavior. In contrast, for thin-film samples, it is governed by a competition between the RKKY and Néel coupling, which can be controlled by the appropriate choice of gap material and thickness on the nanoscale.
The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute
Han, G. C., Wang, C. C., Qiu, J. J., Luo, P. & Ko, V. Interlayer couplings in a differential dual spin valve. Applied Physics Letters 98, 192502 (2011).
Information integration and artificial intelligence for better diagnosis and therapy decisions
24.05.2017 | Fraunhofer MEVIS - Institut für Bildgestützte Medizin
World's thinnest hologram paves path to new 3-D world
18.05.2017 | RMIT University
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy