Rewriting magnetic phase change memory by laser heating

Magnetic phase change memory (MAG PCM) consists of bits with different magnetic permeability values. The bits are read by measuring their effect on a magnetic probe field. Previously low permeability crystalline bits had been written in high permeability amorphous films of Metglas via laser heating. Here data is presented showing that by applying short laser pulses with the appropriate power to previously crystallized regions they can first be vitrified and then again crystallized. Thus, MAG PCM is rewriteable. Technical issues in processing the bits are discussed and results on thermal modeling are presented

Magnetization precession and domainwall structure in cobalt-ruthenium-cobalt trilayers

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width that varies from about 150–60 nm. This behavior is explained in terms of a micromagnetic local-anisotropy model

ESR investigations on Ca perovskite

Electron spin resonance studies on fine powders of La0.65Ca0.35MnO3, performed in the X band, are reported. The coexistence of paramagnetic and ferromagnetic phases, in a narrow temperature range close to the Curie temperature, is observed. The electron spin resonance measurements do not support the presence of bipolarons above the Curie temperature. Temperature dependence of the ESR linewidth is governed by the hopping of polarons and the corresponding activation energy is about 150 meV above Tc

Tunneling magnetoresistance sensors with different coupled free layers

Large differences of magnetic coercivity (HC), exchange coupling field (HE), and tun- neling magnetoresistance ratio (TMR) in magnetic tunnel junctions with different coupled free layers are discussed. We demonstrate that the magnetization behavior of the free layer is not only dominated by the interfacial barrier layer but also affected largely by the magnetic or non-magnetic coupled free layers. All these parameters are sensitively controlled by the magnetic nanostructure, which can be tuned also by the magnetic annealing process. The optimized sensors exhibit a large field sensitivity of up to 261%/mT in the region of the reversal synthetic ferri- magnet at the pinned layers

Plasmon Enhanced Quantum Properties of Single Photon Emitters with Hybrid Hexagonal Boron Nitride Silver Nanocube Systems

Hexagonal boron nitride (hBN) has emerged as a promising ultrathin host of single photon emitters (SPEs) with favorable quantum properties at room temperature, making it a highly desirable element for integrated quantum photonic networks. One major challenge of using these SPEs in such applications is their low quantum efficiency. Recent studies have reported an improvement in quantum efficiency by up to two orders of magnitude when integrating an ensemble of emitters such as boron vacancy defects in multilayered hBN flakes embedded within metallic nanocavities. However, these experiments have not been extended to SPEs and are mainly focused on multiphoton effects. Here, we study the quantum single photon properties of hybrid nanophotonic structures composed of SPEs created in ultrathin hBN flakes coupled with plasmonic silver nanocubes. We demonstrate > 200% plasmonic enhancement of the SPE properties, manifested by a strong increase in the SPE fluorescence. Such enhancement is explained by rigorous numerical simulations where the hBN flake is in direct contact with the Ag nanocubes that cause the plasmonic effects. The presented strong and fast single photon emission obtained at room-temperature with a compact hybrid nanophotonic platform can be very useful to various emerging applications in quantum optical communications and computing

Detection of Iron in Nanoclustered Cytochrome C Proteins Using Nitrogen-Vacancy Magnetic Relaxometry

Nitrogen-vacancy (NV) magnetometry offers an alternative tool to detect iron levels in neurons and cells with a favorable combination of magnetic sensitivity and spatial resolution. Here we employ NV-T1 relaxometry to detect Fe in cytochrome C (Cyt-C) nanoclusters. Cyt-C is a water-soluble protein that contains a single heme group and plays a vital role in the electron transport chain of mitochondria. Under ambient conditions, the heme group remains in the Fe+3 paramagnetic state. We perform NV-T1 relaxometry on a functionalized diamond chip and vary the concentration of Cyt-C from 6 uM to 54 uM, resulting in a decrease of T1 from 1.2 ms to 150 us, respectively. This reduction is attributed to spin-noise originating from the Fe spins present within the Cyt-C. We perform relaxometry imaging of Cyt-C proteins on a nanostructured diamond chip by varying the density of adsorbed iron from 1.44 x 10^6 to 1.7 x 10^7 per um^2

L10 CrPt phase formation and magnetic properties

L10-ordered antiferromagnetic CrPt is of interest as a pinning material in exchange-biased system due to its many intriguing properties and such alloy with a (001) texture has also been used to serve as an underlayer to promote the L10 phase formation of other materials. Therefore, it is important to control not only the L10 phase formation of such material but also the texture of its ordered phase. A systematic study of the L10 phase formation of CrPt thin film was performed. The anisotropy of CrPt L10 phase has also been investigated both experimentally using CrPt/Fe bilayer system and theoretically using first principle calculation. The experimental result is in consistent with the theoretical estimation within the present thin film limitation

Adjusting magnetic nanostructures for high-performance magnetic sensors

The magnetic properties of the soft ferromagnetic layer in magnetic tunnel junctions are one of key factors to determine the performance of magnetoresistance sensors. We use a three-step orthogonal annealing procedure to modify the nanostructures of the free layer in the magnetic tunnel junction to control features such as magnetization reversal, coercivity, exchange field, and tunnel magnetoresistance ratio. We present a sensor with an improved sensitivity as high as 3944%/mT. This magnetic sensor only dissipates 200 lW of power while operating under an applied voltage of 1V