- Klára Uhlířová: The influence of Cu-Mn content on the structural and physical properties of bulk CuMnAs compound
- 23. 10. 2019, 14:10
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
CuMnAs is a room temperature antiferromagnetic semi-metal, which has recently attracted experimental and theoretical interest in the research fields of antiferromagnetic spintronics [1, 2], and physics of Dirac fermions [3]. In the bulk form, the compound is known to have an orthorhombic (Pnma) crystal structure with lattice parameters a = 0.6859 nm, b = 0.3867 nm and c = 0.7320 nm1, while tetragonal structure (P4/nmm) with lattice parameters a = b = 0.3820 nm and c = 0.6318 nm is formed when the materials is grown on GaAs (001) or GaP (001) substrates [2, 4].
Our current studies on bulk Cu-Mn-As system [5] show that the crystal structure and magnetic properties are very sensitive to the exact composition. While stoichiometric CuMnAs has orthorhombic structure and it orders antiferromagnetically below 350-400 K, already less than 10% of the Mn deficiency turns the material to tetragonal phase with similar lattice parameters to thin films and higher Néel temperature than in the orthorhombic case. On the other hand, Mn excess leads to orthorhombic structures with the unit cell doubled along the a-direction (compared to the stoichiometric CuMnAs); this structure was previously reported for CuMn3As2 and Cu2Mn4As3 compounds [6].
From the most stoichiometric tetragonal single crystalline grain, we prepared a transport device using Focused Ion Beam micromachining. This technique allows for precise control over sample geometry and lets us measure the resistivity along arbitrary crystallographic direction. For the first time, we report temperature dependence of both in-plane and out-of-plane resistivity, uncovering large transport anisotropy between both principal crystallographic axes. This is further discussed in context of ab initio calculations assuming various types of impurities in our samples.
- F. Máca et al, J Mag. Mag. Mater. 324 1606-1612 (2012)
- K. Olejník et al. Nature Communications 8 15434 (2017)
- L. Šmejkal et al. Physica Status Solidi RRR 11 1700044 (2017)
- P. Wadley et al., Nature Communications 4 2322 (2013)
- K. Uhlířová et al., J. Alloys Compd. 771, 680 (2019).
- K. Uhlířová et al., J. Alloys Compd. 650 224-227 (2015)