Thermoelectrically Controlled Spin-Switch

The search for novel spintronic devices brings about new ways to control switching in magnetic thin-films. In this work we experimentally demonstrate a device based on thermoelectrically controlled exchange coupling. The read out signal from a giant magnetoresistance element is controlled by exchange coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is shown to vary strongly with changes in temperature, and both internal Joule heating and external heating is used to demonstrate magnetic switching. The device shows no degradation upon thermal cycling. Ways to further optimize the device performance are discussed. Our experimental results show a new way to thermoelectrically control magnetic switching in multilayers.Comment: 4 pages, 4 figure

Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer

Thermal control of exchange coupling between two strongly ferromagnetic layers through a weakly ferromagnetic Ni-Cu spacer and the associated magnetoresistance is investigated. The spacer, having a Curie point slightly above room temperature, can be cycled between its paramagnetic and ferromagnetic states by varying the temperature externally or using joule heating. It is shown that the giant magnetoresistance vanishes due to a strong reduction of the mean free path in the spacer at above ~30 % Ni concentration -- before the onset of ferromagnetism. Finally, a device is proposed and demonstrated which combines thermally controlled exchange coupling and large magnetoresistance by separating the switching and the read out elements.Comment: 4 pages, 4 figure

GHz sandwich strip inductors based on Fe-N Films

Planar strip inductors consisting of two Fe-N films enclosing a conducting film made of Cu, were fabricated on oxidized Si substrates. The inductors were 1mm long, 2 to 100 um wide, with layers of thickness ~0.1 um for the magnetic films and ~0.5 um for the conductor. The soft (Hc=4-8 Oe) magnetic layers were biased during impedance measurement by applying an external field along the strip length thereby facilitating the transverse susceptibility configuration. Biased strips exhibited 70 to 100% inductance enhancement at 1GHz with quality factors Q=4.5 to 3, respectively. The magnetic contribution to the total flux in the narrow devices was less than predicted theoretically, which was attributed to hardening of the magnetic material at the edges of the strip, where the deposition was close to 60 degree incidence. Test films were fabricated on tilted substrates and found to develop a very high anisotropy (up to 1 kOe) for deposition angles larger than 30 degrees. Optimizing the flux closure at the strip edges and using thicker conductor layers is essential for further improving the performance of sandwich strip inductors.Comment: 18 pages, 9 figure

Sub-10 nm colloidal lithography for integrated spin-photo-electronic devices

Colloidal lithography [1] is how patterns are reproduced in a variety of natural systems and is used more and more as an efficient fabrication tool in bio-, opto-, and nano-technology. Nanoparticles in the colloid are made to form a mask on a given material surface, which can then be transferred via etching into nano-structures of various sizes, shapes, and patterns [2,3]. Such nanostructures can be used in biology for detecting proteins [4] and DNA [5,6], for producing artificial crystals in photonics [7,8] and GHz oscillators in spin-electronics [9-14]. Scaling of colloidal patterning down to 10-nm and below, dimensions comparable or smaller than the main relaxation lengths in the relevant materials, including metals, is expected to enable a variety of new ballistic transport and photonic devices, such as spin-flip THz lasers [15]. In this work we extend the practice of colloidal lithography to producing large-area, near-ballistic-injection, sub-10 nm point-contact arrays and demonstrate their integration in to spin-photo-electronic devices.Comment: 15 pages, 5 figure