Fe2P type alloys: an intriguing magnetic playground

Date

Jun 23, 2023

Time

9:00 AM - 10:00 AM

Speaker

Prof. Dr. Ekkes Brück

Affiliation

Delft University of Technology

Language

en

Main Topic

Materialien

Host

Martina Javorka

Description

The Fe2P intermetallic compound, is a prototypical example of a first order ferromagnetic phase transition, known since the 1980s to exhibit a sharp, but weak, FOMT at 216 K (-57°C). In this hexagonal system, the Fe atoms occupy two inequivalent atomic positions, referred to as 3f (in a tetrahedral environment of non-metallic atoms) and 3g (in a pyramidal environment). Also for P we find two distinct lattice sites 1a and 2b. One intriguing aspect is the large uniaxial magnetic anisotropy leading to an anisotropy field of about 7T at 5K. This anisotropy is quite unique for a mainly itinerant electron system as evidenced by the reduction (partial quenching) in the magnetic moments of the iron atoms on the 3f sites when TC is crossed from the ferromagnetic to the paramagnetic state, whereas there is only a limited decrease on the 3g site. This observation has led to a cooperative description of the FOMT, linking the loss of long-range magnetic order at TC with the loss of local moments on the 3f site. Replacing Fe and or P by other elements leads to a rich variety of phenomena. Magnetic ordering temperature and first order character of the phase transition can be either enhanced or reduced. The anisotropy is strongly reduced on reduction of the c lattice parameter and a wide range of compositions display easy-plane anisotropy rather than easy axis, which is favourable for magnetocaloric applications. We will discuss both theoretical and experimental results for a wide range of elements substituting either Fe or P and combined substitutions on both Fe and P sites, while maintaining the hexagonal Fe2P type of structure.

Links

• Seminars at the IFW

Last modified: Jun 13, 2023, 7:39:30 AM