Orthoferrit

Orthoferrites are a class of chemical compounds with the formula RFeO ₃ , where R is one or more rare earth elements . Ortho stands for the orthorhombic crystal structure with the space group Pbnm (space group no. 62, position 3) . Most orthoferrite are weakly ferromagnetic .

The subsystem of the iron ion is actually checkerboard antiferromagnetically ordered with Neel temperatures T _N in the range 620-740  K . The subsystem of rare earth ions is paramagnetic above 5 K and gets its magnetization only through interactions with the iron subsystem. The specialty of the Orthoferrite is an antisymmetric exchange interaction, which is the vector product of neighboring spins in contrast to the usual scalar productincludes. Without this interaction, the Orthoferrite would be antiferromagnetic (with magnetic moment G ). The interaction results in a small tilting of the actually antiparallel magnetized spins in the iron sub-lattice, which makes the orthoferrites to "weak" ferromagnet, with M _s = 100 G . ${\displaystyle 4\pi }$

Furthermore, it is interesting that some of these compounds show a phase transition in which the direction of the antiferromagnetically ordered spins and consequently also the net magnetization rotates by 90 °.

Applications

The combination of high magnetic resonance frequencies with very large magneto-optical effects makes the Orthoferrite interesting objects for the study of laser-induced dynamics. Orthoferrite are transparent and can change the polarization of a light beam under the control of a magnetic field ( Faraday rotation ). This makes them potentially interesting as optical sensors and actuators for use in optical communication. They have also been used as a magnetic material in magnetic bubble memory .

Examples

• Lanthanum Orthoferrite , LaFeO ₃
• Dysprosium Orthoferrite , DyFeO ₃

Individual evidence

1. ^ "Orthoferrit" Oxford English Dictionary, Draft Revision March 2008.
2. ↑ Yuri S. Didosyan et al .: Sensors and actuators on orthoferrites . Proceedings of IEEE Sensors 2004, doi: 10.1109 / ICSENS.2004.1426350 .
3. ↑ Benedict Ita et al .: Magnetic properties of lanthanum orthoferrite fine powders prepared by different chemical routes. Journal of Chemical Sciences 115, 2003, pp. 519-524, doi: 10.1007 / BF02708243 .
4. ↑ A. Maziewski, R. Szymczak: Visual observation of phase domains in dysprosium ortho ferrite. Journal of Physics D: Applied Physics 10, 1977, pp. L37-L38, doi: 10.1088 / 0022-3727 / 10/4/003 .