Superconducting FeSe studied by Mössbauer spectroscopy
This presentation is the property of its rightful owner.
Sponsored Links
1 / 12

Superconducting FeSe studied by Mössbauer spectroscopy and magnetic measurements PowerPoint PPT Presentation


  • 107 Views
  • Uploaded on
  • Presentation posted in: General

Superconducting FeSe studied by Mössbauer spectroscopy and magnetic measurements A. Błachowski 1 , K. Ruebenbauer 1 , J. Żukrowski 2 , J. Przewoźnik 2 , K. Wojciechowski 3 , Z.M. Stadnik 4 1 Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University , Cracow, Poland

Download Presentation

Superconducting FeSe studied by Mössbauer spectroscopy and magnetic measurements

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Superconducting FeSe studied by Mössbauer spectroscopy

and magnetic measurements

A. Błachowski1, K. Ruebenbauer1, J. Żukrowski2, J. Przewoźnik2,

K. Wojciechowski3, Z.M. Stadnik4

1Mössbauer Spectroscopy Division, Institute of Physics,

Pedagogical University, Cracow, Poland

2Solid State Physics Department, Faculty of Physics and Applied Computer Science,

AGH University of Science and Technology, Cracow, Poland

3Department of Inorganic Chemistry, Faculty of Material Science and Ceramics,

AGH University of Science and Technology, Cracow,Poland

4Department of Physics, University of Ottawa, Ottawa, Canada


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Superconducting Materials


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Fe-based Superconducting Families

LaFeAsOFBaFe2As2LiFeAs FeSe

1111 12211111

~55K ~40K ~20K ~10K


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Fe-Se phase diagram

The following phases form close to the FeSe stoichiometry:

1) tetragonal P4/nmm structure similar to PbO, called β-FeSe (or α-FeSe)

2) hexagonal P63/mmc structure similar to NiAs, called δ-FeSe

3) hexagonal phase Fe7Se8 with two different kinds of order, i.e., 3c (α-Fe7Se8) or 4c (β-Fe7Se8)

A tetragonal P4/nmm phase transforms into Cmma orthorhombic phase at about 90 K,

and this phase is superconducting with Tc≈ 8 K.


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Crystal structure of -FeSe

Aim of this contribution is to answer two questions concerned with

tetragonal/orthorhombic FeSe:

1) is there electron spin density (magnetic moment) on Fe ?

2) is there change of electron density on Fe nucleus

during transition from P4/nmm to Cmma structure ?


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Fe1.05Se


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Fe1.05Se


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Magnetic susceptibility measured upon cooling and subsequent warming in field of 5 Oe

- point A - spin rotation in hexagonal phase

- region B- magnetic anomaly

correlated with transition between orthorhombic and tetragonal phases

- point C- transition to the superconducting state


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

tetragonal

phase

transition

orthorhombic

Change in isomer shift S

Change in electron density  on Fe nucleus

S = +0.006 mm/s

ρ = –0.02 electron/a.u.3

orthorhombic

orthorhombic

and

superconducting


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

tetragonal

phase

transition

  • Quadrupole splitting Δ does not change

  • it means that local arrangement of Seatoms around Featom does not change during phase transition

orthorhombic

orthorhombic

orthorhombic

and

superconducting


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Mössbauer spectra obtained in external magnetic field aligned withγ-ray beam

Hyperfine magnetic field is equal to applied external magnetic field.

Principal component of the electric field gradient (EFG) on Fe nucleus

was found as negative.


Superconducting fese studied by m ssbauer spectroscopy and magnetic measurements

Conclusions

1. There is no magnetic moment on iron atoms in the superconducting FeSe.

2. The electron density on iron nucleus is lowered by 0.02 electron/a.u.3

during transition from tetragonal to orthorhombic phase.


  • Login