arXiv subjects

Oren Shafir

Publications and source records attributed to Oren Shafir.

6 recordsLinked to original sources

arXiv2009

The interaction between the magnetic and superconducting order parameters in a La1.94Sr0.06CuO4 wire

We investigate the coupling between the magnetic and superconducting order parameters in an 8 m long meander line ("wire") made of a La1.94Sr0.06CuO4 film with a cross section of 0.5 x 100 um^2. The magnetic order parameter is determined using the Low-Energy muon spin relaxation technique. The superconducting order parameter is characterized by transport measurements and modified by high current density. We find that, when the superconducting order parameter is suppressed by the current, the magnetic transition temperature, Tm, increases. The extracted sign and magnitude of the Ginzburg-Landau coupling constant indicate that the two orders are repulsive, and that our system is located close to the border between first and second order phase transition.

cond-mat.supr-con↗

arXiv2009

Magnetic quantum tunnelling in Fe8 with excited nuclei

We investigate the effect of dynamic nuclear spin fluctuation on quantum tunneling of the magnetization (QTM) in the molecular magnet Fe8 by increasing the nuclei temperature using radio frequency (RF) pulses before the hysteresis loop measurements. The RF pulses do not change the electrons spin temperature. Independently we show that the nuclear spin-spin relaxation time T2 has strong temperature dependence. Nevertheless, we found no effect of the nuclear spin temperature on the tunneling probability. This suggests that in our experimental conditions only the hyperfine field strength is relevant for QTM. We demonstrate theoretically how this can occur.

cond-mat.str-el↗

arXiv2009

Electromagnetic radiation emanating from the molecular nanomagnet Fe8

Photons emitted by transition between the discrete levels of single molecular magnets might obay the elementary condition for Dicke's super-radiance. We investigate this possibility in the Fe8 molecule where magnetization jumps are known to occur at discreet magnetic field values. We found energy bursts each time the molecule undergoes a magnetization jump, confirming their quantum nature. A series of tests indicated that photons carry out the energy, and that indeed these photons obey the elementary conditions for super-radiance.

cond-mat.str-el↗

arXiv2007

Experimental Estimates of Dephasing Time in Molecular Magnets

Muon spin relaxation measurements in isotropic molecular magnets (MM) with a spin value S ranging from 7/2 to 27/2 are used to determine the magnitude and origin of dephasing time $τ_ϕ$ of molecular magnets. It is found that $τ_ϕ$ ~ 10 nsec with no S or ligand dependence. This indicates a nuclear origin for the stochastic field. Since $τ_ϕ$ is a property of the environment, we argue that it is a number common to similar types of MM. Therefore, $τ_ϕ$ is shorter than the Zener and tunneling times of anisotropic MM such as Fe8 or Mn4 for standard laboratory sweep rates. Our findings call for a stochastic Landau-Zener theory in this particular case.

cond-mat.str-el↗

arXiv2005

Demonstrating Multi-bit Magnetic Memory in the Fe8 High Spin Molecule by Muon Spin Rotation

We developed a method to detect the quantum nature of high spin molecules using muon spin rotation, and a three-step field cycle ending always with the same field. We use this method to demonstrate that the Fe8 molecule can remember 6 (possibly 8) different histories (bits). A wide range of fields can be used to write a particular bit, and the information is stored in discrete states. Therefore, Fe8 can be used as a model compound for Multi-bit Magnetic Memory. Our experiment also paves the way for magnetic quantum tunneling detection in films.

cond-mat.other↗

arXiv2005

Universal linear relations between susceptibility and Tc in cuprates

We developed an experimental method for measuring the intrinsic susceptibility χof powder of cuprate superconductors in the zero field limit using a DC-magnetometer. The method is tested with lead spheres. Using this method we determine χfor a number of cuprate families as a function of doping. A universal linear (and not proportionality) relation between Tc and χis found. We suggest possible explanations for this phenomenon.

cond-mat.supr-con↗