Lior Klein

Lior Klein
Bar Ilan University | BIU · Department of Physics

Professor

About

159
Publications
22,036
Reads
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4,347
Citations
Additional affiliations
January 2010 - present
Bar Ilan University
Position
  • Professor (Full)
January 2003 - January 2010
Bar Ilan University
Position
  • Professor (Associate)
October 1997 - January 2003
Bar Ilan University
Position
  • Professor (Assistant)
Education
October 1987 - September 1991
Tel Aviv University
Field of study
  • physics
October 1984 - September 1987
Tel Aviv University
Field of study
  • physics
October 1980 - September 1984
Tel Aviv University
Field of study
  • physics and mathematics

Publications

Publications (159)
Article
Full-text available
We pattern permalloy films into three crossing elongated ellipses with an angle of 60� between the major axes of any pair of ellipses. Planar Hall effect measurements show that the magnetization in the area of overlap of the ellipses has six stable magnetic orientations parallel to the major axes of the three ellipses. We determine the effective an...
Article
Full-text available
We study magnetization reversal of nanostructures of the itinerant ferromagnet SrRuO3 (Tc~150 K). We find that down to 10 K the magnetization reversal is dominated by thermal activation. From 2 - 10 K, the magnetization reversal becomes independent of temperature, raising the possibility for reversal dominated by macroscopic quantum tunneling (MQT)...
Article
Full-text available
We report the fabrication of elliptical planar Hall effect sensors made of Permalloy with response determined by shape-induced uniaxial anisotropy. By using ac excitation and by optimizing the sensor thickness and the amplitude of the excitation current, we have obtained a magnetic field resolution which is better than 600 pT/ √Hz at 1 Hz and close...
Article
Full-text available
We demonstrate current-induced displacement of ferromagnetic domain walls in submicrometer fabricated patterns of SrRuO3 films. The displacement, monitored by measuring the extraordinary Hall effect, is induced at zero applied magnetic field and its direction is reversed when the current is reversed. We find that current density in the range of 10(...
Article
Full-text available
SrRuO3 is endowed with three remarkable features. First, it is a moderately correlated material that exhibits several novel physical properties; second, it permits the epitaxial growth of essentially single-crystal films; and third, because it is a good conductor, it has attracted interest as a conducting layer in epitaxial heterostructures with a...
Article
Full-text available
We use an array of nine elliptical Planar Hall Effect (PHE) sensors and machine learning algorithms to map the magnetic signal generated by a magnetic source. Based on the obtained mapping, the location and nature of the magnetic source can be determined. The sensors are positioned at the vertices of a symmetrical and evenly spaced 3 ª 3 grid. The...
Article
Full-text available
The magnetic field range in which a magnetic sensor operates is an important consideration for many applications. Elliptical planar Hall effect (EPHE) sensors exhibit outstanding equivalent magnetic noise (EMN) on the order of pT/Hz, which makes them promising for many applications. Unfortunately, the current field range in which EPHE sensors with...
Article
Planar Hall effect (PHE) magnetic sensors are attractive for various applications where the field resolution is required in the range of sub-nano Tesla or in Pico Tesla. Here we present a detailed noise study of the PHE sensors consisting of two or three intersecting ellipses. It can be used to measure two axes of the magnetic field in the sensor p...
Article
Full-text available
Droplet‐based lab‐on‐a‐chip systems offer vast possibilities in the manipulation, guidance, tracking, and labeling of individual droplet‐based bioreactors. One of the targeted application scenarios is in drug discovery where millions of unique codes are required, which is out of reach for current technologies. Here, a concept for the realization of...
Article
Flexible sensors are important for applications, such as wearable medical devices, soft robotics, and more, as they can easily conform to soft and irregularly shaped surfaces. This study presents elliptical planar Hall effect magnetic sensors fabricated on a polyamide tape with an equivalent magnetic noise (EMN) better than 200 pT/Hz. The sensor is...
Article
We introduce a planar Hall effect magnetometer in the form of a parallel array of permalloy-based elliptical sensors. The number of ellipses in the array and other fabrication parameters are optimized with the support of numerical simulations. We obtain equivalent magnetic noise (EMN) of 16 pT/Hz at 100 Hz, 25 pT/Hz at 10 Hz, 98 pT/Hz at 1 Hz, and...
Article
Using bilayer films of β-Ta (5 nm)/Ni0.8Fe0.2 (2 nm), we fabricate elliptical structures which exhibit uniaxial magnetic anisotropy, resulting in single magnetic domain behavior. We study induced spin-orbit torques (SOTs) in these devices with first- and second-order harmonic Hall measurements for current flowing along the long axis of the ellipses...
Article
Full-text available
We report a specially designed magnetic field gradiometer based on a single elliptical planar Hall effect (PHE) sensor, which allows measuring magnetic field at nine different positions in a 4 mm length scale. The gradiometer detects magnetic field gradients with equivalent gradient magnetic noises of ∼958, ∼192, ∼51, and ∼26 nT/m√ Hz (pT/mm√Hz) at...
Article
Full-text available
The detection, manipulation, and tracking of magnetic nanoparticles is of major importance in the fields of biology, biotechnology, and biomedical applications as labels as well as in drug delivery, (bio-)detection, and tissue engineering. In this regard, the trend goes towards improvements of existing state-of-the-art methodologies in the spirit o...
Article
Full-text available
We fabricate elliptical planar Hall effect magnetometers with Permalloy thickness ranging between 25 and 200 nm. We study the thickness dependence of their equivalent magnetic noise by examining the effect of the layer thickness on the signal and noise including Joule heating contributions. Sensors with a thickness of 50 nm achieve equivalent magne...
Article
Using planar Hall effect sensors with magnetic flux concentrators, we measure magnetic fields at frequencies below 100 Hz. We show that for a measurement time of up to 100 seconds it is possible to detect fields of ~700 fT and ~1 pT at 10 Hz and 0.1 Hz, respectively. In addition, we measure the linearity and hysteresis of the sensor for fields >2.6...
Article
We present a magnetic tunnel junction (MTJ) where its two ferromagnetic layers are in the form of a single ellipse (SE) and two-crossing ellipses (TCEs). The MTJ exhibits four distinct resistance states corresponding to the four remanent states of the TCE structure. Flowing current in an underlying Ta layer generates in the adjacent TCE structure s...
Article
Full-text available
Magnetofluidics is a dynamic research field, which requires novel sensor solutions to boost the detection limit of tiny quantities of magnetized objects. Here, we present a sensing strategy relying on planar Hall effect sensors in droplet-based micro-magnetofluidics for the detection of a multiphase liquid flow, i.e., superparamagnetic aqueous drop...
Preprint
We present a magnetic tunnel junction (MTJ) where its two ferromagnetic layers are in the form of a single ellipse (SE) and two-crossing ellipses (TCE). The MTJ exhibits four distinct resistance states corresponding to the four remanent states of the TCE structure. Flowing current in an underlying Ta layer generates in the adjacent TCE structure sp...
Article
Using bilayer films of β-Ta/Ni0.8Fe0.2, we fabricate structures consisting of two, three, and four crossing ellipses, which exhibit shape-induced bi-axial, tri-axial, and quadro-axial magnetic anisotropy in the crossing area, respectively. Structures consisting of N crossing ellipses can be stabilized in 2N remanent states by applying (and removing...
Preprint
Full-text available
Using bilayer films of $\beta$-Ta/Ni$_{0.8}$Fe$_{0.2}$, we fabricate structures consisting of two, three and four crossing ellipses which exhibit shape-induced bi-axial, tri-axial and quadro-axial magnetic anisotropy in the crossing area, respectively. Structures consisting of N crossing ellipses can be stabilized in 2N remanent states by applying...
Article
Full-text available
Spin-orbit torques emerge as a promising method for manipulating magnetic configurations of spintronic devices. Here, we show that these torques can induce a magnetization reversal via domain wall propagation which may open new ways in developing novel spintronic devices and in particular in realizing high-density multi-level magnetic memory. Our d...
Article
We integrate elliptical planar Hall effect (PHE) magnetometers with optimized, high permeability magnetic flux concentrators. The integrated magnetometers exhibit at room temperature an equivalent magnetic noise of ∼5 pT/√Hz at 10 Hz, 7.4 pT/√Hz at 1 Hz, and better than 100 pT/√Hz at 10 mHz. The results constitute more than an order of magnitude im...
Article
We study the anomalous Hall effect (AHE) and anisotropic magnetoresistance (AMR) in a series of ultra-thin Pt/Co(x)/Pt trilayers (0.1nm⩽x⩽0.5nm). We find that the AHE exhibits a significant increase at low temperatures (T). This increase cannot be attributed to a trivial increase in magnetization or resistivity. A similar T dependence is observed i...
Article
Full-text available
Applying stress to a ferroelastic material results in a nonlinear strain response as domains of different orientations mechanically switch. The ability to write, erase and move domain walls between such ferroelastic domains suggests a method for making nanoelectronics where the domain wall is the device. However, little is known about the magnetic...
Article
Full-text available
Spintronic devices often require the ability to locally change the magnetic configuration of ferromagnetic structures on a sub-micron scale. A promising route for achieving this goal is the use of heavy metal/ferromagnetic heterostructures where current flowing through the heavy metal layer generates field-like and anti-damping like torques on the...
Preprint
The sheet resistance Rs of Ar+ irradiated SrTiO3 in patterns with a length scale of several microns increases significantly below 40 K in connection with driving currents exceeding a certain threshold. The initial lower Rs is recovered upon warming with accelerated recovery around 70 and 160 K. Scanning superconducting quantum interference device m...
Chapter
Full-text available
The planar Hall effect (PHE) is intimately related to the anisotropic magnetoresistance (AMR). However, while AMR-based magnetic sensors have been commercially available for decades and are widely used in a variety of applications, PHE-based sensors have been mostly the subject of research. The reason for that is most probably the superior performa...
Article
A unique readout circuit topology aimed at integration with a novel type of magnetic random access memory (MRAM) is presented. The properties of the new MRAM bitcell are introduced, and the specifics of the circuit used to interface with the CMOS circuitry are described. The noise transfer function and effectiveness of the proposed topology with it...
Article
SrRuO3 films have large uniaxial magnetocrystalline anisotropy tilted out of the film plane. When cooled in zero field from above the Curie temperature (∼150 K), a magnetic domain structure emerges in the form of 200-nm-wide stripes oriented along the in-plane projection of the magnetic easy axis. We measure the interface resistance of the magnetic...
Article
The sheet resistance Rs of Ar+ irradiated SrTiO3 in patterns with a length scale of several microns increases significantly below ∼40 K in connection with driving currents exceeding a certain threshold. The initial lower Rs is recovered upon warming with accelerated recovery around 70 and 160 K. Scanning superconducting quantum interference device...
Patent
Full-text available
The present invention discloses plural planar Hall-effect sensors each having a magnetic sensing region of an elongated shape, the magnetic sensing regions having plural orientations, wherein, for a ratio of long axis length to short axis length greater than a predetermined number, effective single magnetic domain behavior is exhibited in the sensi...
Article
Full-text available
Recent reports have demonstrated field resolutions of planar Hall effect magnetometers in the picotesla range. Here, we report a significant improvement in the field resolution of these sensors by decreasing their preamplifier white noise and the sensing element 1/ f noise. We design, build, and test a miniature transformer-matched amplifier with a...
Article
Full-text available
We study the thermal stability of the magnetization states in permalloy microstructures in the form of two crossing elongated ellipses, a shape which yields effective bi-axial magnetic anisotropy in the overlap area. We prepare the structure with the magnetization along one of the easy axes of magnetization and measure the waiting time for switchin...
Article
Full-text available
We present a composed planar Hall effect sensor with two modes of operation: (a) an ON mode where the composed sensor responds to magnetic field excitations similarly to the response of a regular planar Hall effect sensor, and (b) an OFF mode where the response is negligible. The composed planar Hall effect sensor switches from the OFF mode to the...
Article
Full-text available
The Hall effect resistivity rho(xy) of high-quality films of the itinerant ferromagnet SrRuO3 was measured at low temperatures. SrRuO3 films have large uniaxial magnetocrystalline anisotropy, and in the relevant temperature range the easy axis is 30 degrees degrees from the film normal. We measure changes in rho(xy) associated with changes in the o...
Article
Full-text available
Patterned nanostructures on the order of 200 nm $\times$ 200 nm of the itinerant ferromagnet ${\rm SrRuO_3}$ give rise to superparamagnetic behavior below the Curie temperature (${\rm \sim 150 \ K}$) down to a sample-dependent blocking temperature. We monitor the superparamagnetic fluctuations of an individual volume and demonstrate that the field...
Article
Full-text available
We study the anisotropic magnetoresistance and planar Hall effect of La0.8Sr0.2MnO3 when the field is rotated out of the film plane. We fit the data with a model, which consists of two independent contributions related to (a) the orientation of the magnetization relative to the crystal axes and (b) the orientation of the magnetization relative to t...
Article
Full-text available
We measure the anomalous Hall effect (AHE) in several patterns of the itinerant ferromagnet ${\text{SrRuO}}_{3}$ before and after the patterns are irradiated with electrons. The irradiation increases the resistivity of the patterns due to the introduction of point defects and we find that the AHE coefficient ${R}_{s}$ scales with the total resistiv...
Article
Full-text available
We report a systematic study of the thickness dependence of the resistivity tensor of epitaxial thin films of magnetite (Fe3O4). We find that decreasing film thickness decreases the relative magnitude of the terms related to crystal symmetry but increases their field dependence. We attribute this behavior to the presence of antiphase boundaries in...
Article
Full-text available
SrRuO3 is an itinerant ferromagnet with a Curie temperature of 150 K and a uniaxial magnetocrystalline anisotropy. Using high-quality epitaxial thin films, we measure at 2 K the anisotropic magnetoresistance and the planar Hall effect as a function of the in-plane current direction and the magnetization orientation. We identify three types of contr...
Article
Full-text available
We inject a sequence of 1 ms current pulses into uniformly magnetized patterns of the itinerant ferromagnet SrRuO3 until a magnetization reversal is detected. We detect the effective temperature during the pulse and find that the cumulative pulse time τ required to induce magnetization reversal depends exponentially on 1/T. In addition, we find tha...
Article
Full-text available
Patterned structures of ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ that exhibit a decrease in their electrical conductivity below 30 K recover their higher conductivity upon warming in a thermally activated process. Two dominant energy barriers ${E}_{b}$ are identified: ${E}_{b1}=0.224\ifmmode\pm\else\textpm\fi{}0.003$ eV related to conductivity r...
Article
Full-text available
We have measured the change in the resistivity of thin films of SrRuO3 and CaRuO3 upon introducing point defects by electron irradiation at low temper- atures, and we find significant deviations from Matthiessen's rule. For a fixed irradiation dose, the induced change in resistivity decreases with increasing temperature. Moreover, for a fixed tempe...
Article
Full-text available
We find that the Hall effect resistivity ($\rho_{xy}$) of thin films of \lsmo\ varies as a function of the angle $\theta$ between the applied magnetic field and the film normal as $\rho_{xy}=a\cos \theta + b\cos 3\theta$, where $|b|$ increases with increasing temperature and decreases with increasing magnetic field. We find that the angular depende...
Article
Full-text available
We find that the Hall effect resistivity (${$\rho${}}_{xy}$) of thin films of La${}_{0.8}$Sr${}_{0.2}$MnO${}_{3}$ varies as a function of the angle $$\theta${}$ between the applied magnetic field and the film normal as ${$\rho${}}_{xy}=a\mathrm{cos}$\theta${}+b\mathrm{cos}3$\theta${}$, where $|b|$ increases with increasing temperature and decreases...
Article
Full-text available
We extract the paramagnetic anomalous Hall effect (AHE) resistivity ${$\rho${}}_{xy}^{\mathrm{AHE}}$ in thin films of the itinerant ferromagnet SrRuO${}_{3}$ and show that the AHE coefficient ${R}_{s}$ scales with the longitudinal resistivity ${$\rho${}}_{xx}$. We fit the resistivity dependence of ${$\rho${}}_{xy}^{\mathrm{AHE}}$ assuming two mecha...
Article
Full-text available
We find that the sheet resistance (Rs) of patterned samples of LaAlO3/SrTiO3 with a length scale of several microns may increase significantly at low temperatures in connection with driving electrical currents and applying in-plane magnetic fields. As the samples are warmed up, Rs recovers to its original value with accelerated recovery near 70 K a...
Article
Full-text available
We inject current pulses into uniformly magnetized patterns of thin films of the itinerant ferromagnet SrRuO3, while monitoring the effective temperature of the patterns during the current injection. We gradually increase the amplitude of the pulses until magnetization reversal occurs. We observe magnetization reversal induced by current above a te...
Article
Full-text available
We show that shape anisotropy induces effective single domain behavior in elliptical structures of thin permalloy films with long axis ranging between several microns to several millimeters, provided that the ratio of the film long and short axes is large enough. We also show that the thin film elliptical structures exhibit a wide range of effectiv...
Article
Full-text available
We pattern submicrometer structures of thin films of permalloy in the form of two crossing ellipses and in the form of one long ellipse crossed by several ellipses where the width of the ellipses varies between 100 and 1000 nm. We find that the crossing area has two stable axes of magnetization, which are perpendicular to each other and which are r...
Article
Full-text available
SrRuO3 is an itinerant ferromagnet (Tc ∼ 150K) characterized by large uniaxial magnetocrystalline anisotropy (K1 ∼ 7.7×106erg/cm3) and relatively low saturation magnetization (Ms = 213emu/cm3) - properties which make SrRuO3 an extremely hard magnetic material. We have patterned arrays of rectangular nanoislands of a high quality epitaxial film of S...
Article
The anomalous Hall effect (AHE) is an intriguing magnetotransport phenomenon linked to various intrinsic and extrinsic mechanisms. While for some conductors quantitative understanding of this phenomenon has been achieved, the understanding of the AHE in the manganites is far from comprehensive. We measured the transverse resistivity (ρxy) of thin f...
Article
Full-text available
We measure the anomalous Hall effect (AHE) resistivity ρxy in thin films of the itinerant ferromagnet SrRuO3. At low temperatures, the AHE coefficient Rs varies with ρxx2, and at higher temperatures, Rs reaches a peak and then changes sign just below Tc. We find that for all films studied, Rs scales with resistivity in the entire ferromagnetic phas...
Preprint
We measure the anomalous Hall effect (AHE) resistivity $\rho_{xy}$ in thin films of the itinerant ferromagnet SrRuO$_{3}$. At low temperatures, the AHE coefficient $R_{s}$ varies with $\rho_{xx}^2$, and at higher temperatures, $R_{s}$ reaches a peak and then changes sign just below $T_{c}$. We find that for all films studied $R_{s}$ scales with res...
Article
Full-text available
A systematic study of the temperature and magnetic field dependence of the longitudinal and transverse resistivities of epitaxial thin films of magnetite (Fe3O4) is reported. The anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) are sensitive to the in-plane orientation of current and magnetization with respect to crystal axes in...
Article
Full-text available
We measure the anomalous Hall effect (AHE) resistivity $\rho_{xy}$ in thin films of the itinerant ferromagnet SrRuO$_{3}$. At low temperatures, the AHE coefficient $R_{s}$ varies with $\rho_{xx}^2$ in agreement with side jumps and Berry phase models. At higher temperatures, $R_{s}$ reaches a peak and then changes sign just below $T_{c}$. We find th...
Article
Full-text available
We study the magnetoresistance (MR) of the quasi-2-D electron liquid at the interface that forms between SrTiO<sub>3</sub> and LaAlO<sub>3</sub> as a function of the magnitude and orientation of the magnetic field. We find that at T ¿ 60 K, the MR is described by a + b cos<sup>2</sup> ¿ + c sin<sup>2</sup> ¿ cos<sup>2</sup> ¿, where ¿ is the a...
Article
Full-text available
We present planar Hall effect measurements of elliptical permalloy sensors having different aspect ratios and thicknesses along with extensive numerical simulations and analytical analysis. We identify an upper limit for the sensor minor axis on the order of 1 μ m above which hysteresis effects intensify. We also find that the increased ratio betwe...
Article
This work represents a new method to synthesis of ZnO and/or Zn nanoparticles by means of microwave plasma whose electrons are the reducing agents. Glass quadratic slides sized 2.5 x 2.5 cm were coated by ZnO and/or Zn particles whose sizes ranged from a few micrometers to approximately 20 nm. The size of the particles can be controlled by the type...
Article
We demonstrate herein the coating of dielectric surfaces with metallic thin films using the plasma-reduction of metallic ions such as HAuCl4, AgNO3, H2PtCl6, PdCl2, Ni(NO3)2 and Co(NO3)2 in solutions. Stable plasma was formed using 12MHz/18W and 2.45GHz/900W plasma generators and was confined in a Pyrex vacuum chamber with an inert gas environment....
Article
Full-text available
The longitudinal resistance Rxx of the SrTiO3/LaAlO3 interface with magnetic fields applied perpendicular to the interface has an antisymmetric term [namely, Rxx(H)≠Rxx(−H)] which increases with decreasing temperature and increasing field. We argue that the origin of this phenomenon is a nonhomogeneous Hall effect with clear contribution of an extr...
Preprint
SrRuO3 is an itinerant ferromagnet with orthorhombic structure and uniaxial magnetocrystalline anisotropy - features expected to yield resistivity anisotropy. Here we explore changes in the resistivity anisotropy of epitaxial SrRuO3 films due to induced magnetization in the paramagnetic state by using the planar Hall effect. We find that the effect...
Article
We present a new technique, the solvent-assisted deposition in plasma (SADIP), for the coating glass slides by 34 ± 16 nm sized zinc nanoparticles. Using this method glass was coated by a very dense and homogeneous layer of nanoparticles. In addition, zinc nanoparticles did not oxidize rapidly, as can be expected, due to their low reduction potenti...
Article
Full-text available
We measured the anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) in a [001] oriented epitaxial thin film of La <sub>0.7</sub> Ca <sub>0.3</sub> MnO <sub>3</sub> (LCMO) as a function of magnetic field, temperature, and current direction relative to the crystal axes. We find that both AMR and PHE in LCMO depend strongly on the cur...