1) How one can describe short range and long range ferromagnetic ordering by analysing M(T,H) data?
2) is superexchange always short-range order?
3) how to idetify the type of exchange interaction in the magnetism shown by a system?
4) Does superexchange has some relationship among magnetic parameters (such as Curie tempeature, doping concentration, carrier concentration)?
Direct exchange may be responsible of long range ferromagnetic which is translated by:
-susceptibility peak at TC
-spontaneous magnetization decreasing vs T
-rapid saturation magnetization in M-H curves
Super-exchange comes usually through a "bridge" (presence of non magnetic ions as O2-, F-, Cl-....), so its presence can be reflected on the above curves :
-additional anomaly in susceptibility X(T), deviation from the Curie-Weiss law of 1/X above Tc with a net curvature
- spontaneous magnetization is also influenced, it decreases with eventual anomalies (knee, crease, shoulder,..)
-M-H can exhibit jumps or plateaus before saturation.
Some common models take into account direct and super-exchange couplings (J1-J2 Heseinberg,...)
Hi!
The M(T,H) traces can be as well impacted by anisotropy parameters. So it is not obvious to state on short to long range ordering from such traces. However as said by M. El Hafidi, additional anomaly in susceptibility X(T), deviation from the Curie-Weiss law of 1/X above Tc with a net curvature is a best way to anticipate on short range ordering since the anisotropic contributions normally fail in the Tc temperature range. Also the crystal structure (cubic to low symmetry).could be a cause on non isotropic exchange interaction forces.
Kind regards
Daniel
- Badges
- Science topic
- Similar topics
- Physics
- Condensed Matter Physics