Chiral helicene, a fully conjugated system without stereogenic carbon, can filter spins effectively at room temperature, a consequence of the chiral-induced spin-selectivity effect. The chirality dictates the spin of the electrons transferred through helicene, and magnetoresistance devices based on these molecules show antisymmetric magnetoresistance versus H plots.

Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices.

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic–inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material.

Conductive organic polymers are used in organic electronic devices and specifically in organic-based light-emitting diodes (OLEDs). It is expected that by controlling the spin of the electrons that are injected from and into these devices, their energy efficiency will increase significantly. However, it is commonly thought that this would require introducing ferromagnets into the device, which represents a technological challenge. We present data indicating that electron transport through a chiral conductive polymer is highly spin dependent; hence, the polymers themselves can serve as a spin filter and in principle, this may allow the operation of spin-OLED without any magnetic component

Spin injection into solid-state devices is commonly performed by use of ferromagnetic metal electrodes. Here, we present a spin injector design without permanent magnet; rather, the spin selectivity is determined by a chiral tunneling barrier. The chiral tunneling barrier is composed of an ultrathin Al2O3 layer that is deposited on top of a chiral self-assembled monolayer (SAM), which consists of cysteine or oligopeptide molecules. The experimentally observed magnetoresistance can be up to 20% at room temperature, and it displays an uncommon asymmetric curve as a function of the applied magnetic field. These findings show that the spin injector transmits only one spin orientation, independent of external magnetic field. The sign of the magnetoresistance depends on the handedness of the molecules in the SAM, which act as a spin filter, and the magnitude of the magnetoresistance depends only weakly on temperature.

A new type of device is presented that allows direct measurement of spin selectivity in charge transfer processes occurring in adsorbed molecules. The new device provides direct information about the nature of the charge being transferred (electrons or holes) and on spin selectivity, if it exists. Here the device is applied for establishing the spin-dependent electron transfer through double-stranded DNA and its variation with the length of the oligomer. The DNA is self-assembled on a silver substrate and is measured under ambient conditions. The device is based on monitoring the electric potential between a ferromagnetic Ni layer and a silver layer, on top of which the DNA is self-assembled. When a dye molecule, attached to the DNA, is photoexcited, a charge transfer between the dye and the silver substrate takes place, resulting in a change in the electric potential between the Ni and the silver. If the charge transfer is spin selective, the electric potential measured depends on the direction of magnetization of the Ni.

We demonstrate that the average nanocrystallite size and size distribution can be used as control parameters to respectively tune the peak value and the width-at-half-maximum of the isothermal magnetic entropy change or the adiabatic temperature change during the magnetization process (magnetocaloric effect) such that a reasonably large relative cooling power, conducive to magnetic refrigeration, is achieved.

The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.