Lattice dynamics of the high-entropy Zn1-xMnxTe magnetic semiconductor alloy – Inelastic light/neutron scattering

7 Mar 2024
Job Information

Organisation/Company

Olivier Pagès

Research Field

Physics

Researcher Profile

Recognised Researcher (R2)
Leading Researcher (R4)
First Stage Researcher (R1)
Established Researcher (R3)

Country

France

Application Deadline

29 Apr 2024 – 22:00 (UTC)

Type of Contract

Temporary

Job Status

Full-time

Offer Starting Date

1 Oct 2024

Is the job funded through the EU Research Framework Programme?

Not funded by an EU programme

Is the Job related to staff position within a Research Infrastructure?

No

Offer Description

Lattice dynamics of the high-entropy Zn1-x Mnx Te magnetic semiconductor alloy –

Inelastic light/neutron scattering

 

Due to their simple structure (two bond species randomly arranged on a cubic lattice), the zincblende A1‑x Bx C semiconductor alloys (SCA) set a benchmark to explore how physical properties are impacted by disorder. In particular, the vibrational properties governed by the bond force constant potentially offer a suitable probe at the ultimate atom scale (where the atom substitution occurs). A longstanding controversy since the emergence of SCA in the 1960s was whether the vibration of a given bond is “blind” to the alloy disorder, i.e., generates a unique mode at any composition (like in the AC and BC compounds), or actually “sees” the alloy disorder, i.e., diversifies into a multi-mode signal (to clarify in terms of number and nature of modes) reflecting inherent fluctuations in the alloy composition at the local scale. Over the past decade and half our group introduced the percolation model (PM [1]) that distinguishes between like bonds depending on whether they vibrate in “same” or “alien” environments. The PM has been tested and validated on the phonon and phonon-polaritons of various well-matched/WM and highly-mismatched/HM SCA, hence, solving the controversy in favor of the second scenario, apparently.

In this PhD-project we shift the focus from the now well-understood WM/HM-SCA to tackle the magnetic Zn1 xMnx-SCA (with Mn as the magnetic species), using Zn1-xMnxTe as a case study [2,3]. High-quality large-size free-standing Zn1-xMnxTe single crystals will be grown specially for the project over a large x-domain (x≤0.8) by the Bridgman method [4].
Regarding phonons, the 3d orbital hybridizes into the tetrahedral Mn-bonds but not in Zn-bonds – because the 3d electrons are less tightly bound in Mn than in Zn. This fragilizes the crystal structure of Zn1-xMnx-based M-SCA,4 exalting the vibrational properties and possibly leading to an “exotic” phonon behavior. In fact, the Raman signal of Zn1-xMnxTe is assigned in terms of the rare intermediary (hence undetermined) type in the historical classification of the phonon mode behavior of SCA [2,3,5]. This might reflect a lack of understanding, which stimulates a careful re-examination within the PM. As for the phonon-polaritons of Zn1-xMnxTe, they remain unexplored. ZnTe-based SCA exhibit a large band gap and hence are transparent to the visible laser excitation. This offers a chance to study their phonon-polaritons by forward Raman scattering (schematically operating in “transmission”). Last, large Mn incorporation might generate a collective magnetic excitation, i.e., a magnon, likely to be detected by Raman (as observed with Cd1-xMnxTe [6]) as well as neutron (as observed with MnTe [7]) scattering. 
Generally, our ambition is to achieve a coherent fundamental study of the collective dynamic excitations (phonons, phonon-polaritons, magnon) of Zn1-xMnxTe throughout the entire Brillouin zone, i.e., from the zone-center phonon-polaritons up to the zone-edge phonons/magnon, by combining inelastic light (Raman) scattering and inelastic neutron scattering, with high-pressure Raman/X-ray-diffraction (using a diamond anvil cell) and ab initio phonon calculations in support.
The PhD student will be at the center of the project taking place within the wall-less international laboratory ViSA-IRP (Vibrations of Semiconductor Alloys – International Relationship Project, 2024 – 2028) funded by the LUE (Lorraine University of Excellence) program. She/he will be directly involved/in charge of the crystal growth (Toruń, Poland), in (high-pressure) Raman measurements (Metz) and in all measurements done on national facilities, to be done in collaboration: high-pressure X-ray diffraction (using the SOLEIL or ESRF synchrotron sources, France) and inelastic neutron scattering (using the ILL neutron reactor – France) – the access to national-size facilities being conditioned to proposal acceptance. Though the PhD project is mostly experimental in nature, the student will also be involved in ab initio phonon calculations (SIESTA code [8], Metz) coming in support of the discussion of all vibrational data. 

References: [1] Pagès et al. Phys. Rev. B 77, 125208 (2008); [2] Peterson et al., Phys. Rev. B 33, 1160 (1986); [3] Talwar et al., Materials Chemistry and Physics 220, 460 (2018); [4] Strzałkowski et al., Materials 16, 3945 (2023); [5] Oles et al., J. Phys. C: Solid State Phys. 18, 6289 (1985); [6] Venugopalan et al., Phys. Rev. B 25, 2681 (1982); [7] Szuskiewicz et al., Phys. Stat. Sol. C 3, 1141 (2005); [8] Garcia et al., J. Chem. Phys. 512, 204108 (2020).
 

Funding category: Contrat doctoral
LUE (Lorraine Université Excellence) PhD grant
PHD title: Doctorat de physique de la matière condensée
PHD Country: France

Requirements
Specific Requirements

Master in condensed matter physics.

 

Additional Information
Work Location(s)

Number of offers available

1

Company/Institute

Olivier Pagès

Country

France

City

Metz

Geofield

Where to apply

Website

https://www.abg.asso.fr/fr/candidatOffres/show/id_offre/120911

Contact

Website

http://lcp-a2mc.univ-lorraine.fr/

STATUS: EXPIRED