Zero Thermal Expansion in Magnetic and Metallic Tb(Co,Fe)2 Intermetallic Compounds.

Due to the advantage of invariable length with temperatures, zero thermal expansion (ZTE) materials are intriguing but very rare especially for the metals based compounds. Here, we report a ZTE in the magnetic intermetallic compounds of Tb(Co,Fe)2 over a wide temperature range (123-307 K). A negligible coefficient of thermal expansion (αl = 0.48 × 10-6 K-1) has been found in Tb(Co1.9Fe0.1). Tb(Co,Fe)2 exhibits ferrimagnetic structure, in which the moments of Tb and Co/Fe are antiparallel alignment along the c axis. The intriguing ZTE property of Tb(Co,Fe)2 is formed due to the balance between the negative contribution from the Tb magnetic moment induced spontaneous magnetostriction and the positive role from the normal lattice expansion. The present ZTE intermetallic compounds are also featured by the advantages of wide temperature range, high electrical conductivity, and relatively high thermal conductivity.