“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Independent magnetic ordering of the Er and Fe sublattices in ErFe6Sn6

J.M. Cadogan and D.H. Ryan

Department of Physics and Astronomy, University of ManitobaWinnipeg, MB, R3T 2N2, Canada

E-mail: cadogan@physics.umanitoba.ca

Department of Physics, McGill UniversityMontreal, QC, H3A 2T8, Canada E-mail: dhryan@physics.mcgill.ca

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

ErFe6Sn6

• ErFe6Sn6 is orthorhombic (Cmcm)

• There are two Er sites, five Fe sites and ten Sn sites

• RFe6Ge6 and RFe6Sn6 intermetallics

show the somewhat unusual phenomenon of independent magnetic ordering of the R and Fe sublattices [1].

• Fe orders antiferromagnetically at 555 K. The Er ordering takes place at 5 K, without affecting the Fe order [2].

• The Er is located between ferromagnetic planes of Fe, whose antiferromagnetic interplanar coupling leads to a zero net exchange field at the Er site.

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

I=2

Mössbauer spectroscopy of 166Er

The 80.6 keV Mössbauer gamma-ray arises from the transition between the I=2 excited nuclear state and the I =0 ground state of the 166Er nucleus.

166Ho 27 hr

166Er

80.6 keV, 1.9 ns

0 keVI=0

−

A more detailed description of the 166Er experiment can be found in our article on Er3Ge4

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Fe magnetic ordering at 555 K detected by Differential Scanning Calorimetry

Er magnetic ordering at 5 K detected by ac-susceptibility

Magnetic ordering in ErFe6Sn6

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Magnetization of the Er sublattice

• Magnetometry at 2 K shows that the Er sublattice magnetic order comprises both FM and AF components

• M remains unsaturated up to 9 T.

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Neutron powder diffraction

Hahn-Meitner Institute, Berlin

The magnetic scattering from the Er sublattice is quite weak.

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

A Mössbauer triptych

166Er

57Fe

119Sn

Note the different

velocity scales!

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

• The 57Fe Mössbauer spectrum shows the (AF) order of the Fe sublattice, with an Fe moment of 1.7 B at RT.

• The 119Sn Mössbauer spectrum shows two components, one of which is magnetically split. Sn is non-magnetic so the Sn nuclei only see transferred hyperfine fields from their (magnetic) surroundings. The relative areas of the two components in the 119Sn Mössbauer spectrum are fully consistent with the magnetic structures of the Er sublattices (sites) determined by neutron diffraction. As such, the 119Sn Mössbauer work provides an excellent verification of the neutron diffraction results.

• The 166Er Mössbauer spectrum obtained at 2 K shows that the Er3+ magnetic moment in ErFe6Sn6 is 8.5(1) B, close to its free-ion value (9 B)

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Er sublattice magnetic order in ErFe6Sn6

Er 4c1 site.

Er 4c2 site.

Open circles represent the z =1/4 plane, Hatched circles represent the z =3/4 plane.

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

References

• This study demonstrates the powerful complementarity of Mössbauer Spectroscopy (a local magnetic probe) and Neutron Diffraction (an extended-scale measurement)

• Neutron diffraction gives the FM and AF components of the magnetic order

• 166Er Mössbauer Spectroscopy gives the total local Er3+ moment.• 57Fe Mössbauer Spectroscopy gives the total local Fe moment.• 119Sn Mössbauer Spectroscopy provides verification of the magnetic

structure.

[1] J.M. Cadogan and D.H. Ryan, J. Alloys. Comp. 326, 166-73 (2001)

[2] J.M. Cadogan et al. J. Phys.: Condensed Matter 15, 1757-71 (2003)