posted on 2016-11-29, 19:34authored byRoman A. Khalaniya, Andrei V. Mironov, Valeriy Yu. Verchenko, Anton Jesche, Alexander A. Tsirlin, Andrei V. Shevelkov
A new
phase Fe32+δGe33As2 (δ
≤ 0.136) was obtained by two-step synthesis from the elements.
Fe32+δGe33As2 crystallizes
in its own structure type (space group P6/mmm, Z = 1, a = 11.919(3)
Å, c = 7.558(4) Å) that can be described
as a recurrent two-dimensional intergrowth of two intermetallic structure
types, MgFe6Ge6 and Co2Al5. Their blocks are represented by infinite columns in the structure.
No visible structural changes were observed in the temperature range
from 10 to 300 K. At 125 K, Fe32+δGe33As2 undergoes an antiferromagnetic-like transition, while
above 150 K it shows a typical Curie–Weiss paramagnetic behavior.
Below the transition temperature, a peculiar field-dependent magnetic
susceptibility, that shows a significant increase of the susceptibility
upon increasing the magnetic field, and a change in transport properties
have been observed. Above 140 K, Fe32+δGe33As2 reveals a metallic behavior, in agreement with electronic
structure calculation, while below this point the resistivity nonmonotonically
increases upon cooling. The Seebeck coefficient is positive, indicating
that holes are the major charge carriers, and shows a broad maximum
around 57 K.