Borides Mn_3-x{Rh,Ir}₅B₂ with Ti₃Co₅B₂-type: X-ray single crystal and TEM data, physical properties

Author(s)

Gerda Rogl, Markus Eiberger, Soner Steiner, Herwig Michor, Jiri Bursik, Gerald Giester, Andriy Grytsiv, Peter Franz Rogl

Abstract

A cursory investigation of the phase relations in the Mn-{Rh,Ir}-B systems prompted for each system a ternary compound, Mn_3-x{Rh,Ir}₅B₂, the crystal structure of them was determined from X-ray single crystal data to be isotypic with the Ti₃Co₅B₂-type (space group P4/mbm, No. 127). In both cases the Mn-site in 2a

at the origin of the unit cell exhibits a significant defect (or Mn/B

substitution). Transmission electron microscopy studies confirm the

absence of a superstructure related to these defects/disorder. The two

phases, Mn_3-xRh₅B₂ (x∼0.34) and Mn_3-xIr₅B₂

(x∼0.85) at 950 °C show rather limited homogeneity regions pointing

towards higher Mn-contents. Whereas temperature dependent magnetization

and specific heat measurements of Mn_2.15Ir₅B₂

do not reveal any indication for a magnetic phase transition in the

temperature range from 3 to 300 K, a broad specific heat anomaly at

around 200 K and a tilde shape of the temperature dependent

magnetization of Mn_2.66Rh₅B₂ appears

indicative of an antiferromagnetic phase transition. The latter is also

reflected by an anomaly of the electrical resistivity (ρ; 4–300 K) of Mn_2.66Rh₅B₂ which displays a non-monotonous temperature dependence, whereas ρ(T) of Mn_2.15Ir₅B₂

displays a simple metallic-like behavior dominated by scattering from

defects. Elastic moduli and Poisson's ratio were determined at room

temperature from Resonant Ultrasonic Spectroscopy (RUS) data yielding

Young's moduli of E ∼ 170 GPa for Mn_2.66Rh₅B₂ and E ∼ 210 GPa for Mn_2.15Ir₅B₂. Vickers hardness HV is lower for Mn_2.66Rh₅B₂ (HV = 590 ≅ 5.79 GPa) than for Mn_2.15Ir₅B₂ (HV = 655 ≅ 6.42 GPa). The indentation fracture toughness for Mn_2.15Ir₅B₂ was IK_C = 0.71 ± 0.5 MPa m^1/2.

Organisation(s)

Department of Materials Chemistry, Department of Mineralogy and Crystallography

External organisation(s)

Technische Universität Wien, Czech Academy of Sciences

Journal

Solid State Sciences

Volume

154

Pages

1-7

No. of pages

7

ISSN

1293-2558

DOI

https://doi.org/10.1016/j.solidstatesciences.2024.107583

Publication date

08-2024

Peer reviewed

Yes

Austrian Fields of Science 2012

105116 Mineralogy, 104011 Materials chemistry, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Condensed Matter Physics, General Chemistry, General Materials Science

Portal url

https://ucrisportal.univie.ac.at/en/publications/82be73e2-d70d-4c12-b585-46b3fdd1fd2b