Energy levels for a pair of antiferromagnetically coupledS = 5/2 spins. The arrows show the transitions between the levels that are allowed in inelastic neutron scatteringevents.

Note that in a single scattering act the totalspin can change onlyby S = ±1 (can you explain why?)

tot

Schematic of a time-of-flight inelastic neutron scatteringspectrometer − a perfect tool for investigating

dispersionless excitations in solid:

Disk chopper

This is one of the instruments we use:

The idea worked, and even though the FM coupling induced byholes was weak, the information the measurement yielded wasreally valuable

People are trying to figure out the rules that govern the Mn-Mn NN exchange in dilute alloys derived from the II-VI compound family (ZnO, ZnS, ZnSe, ZnTe,CdS, CdSe, CdTe, HgS, HgSe, HgTe).

Zn1-xMnxTe (x = 2%)=4.8Å, T= 40K

• J1atm= -0.795 meV

• J4Katm=-0.836 meV

• 5% Energy Shift• 0.49% Lattice

Compression

E=0.158 meV • |2|1 Transition

Our data show that the “tendency line” based on the entire family definitely is not a universal characteristic, because the J(r) depen-dence in individual compounds from the (II,Mn)-VI family is deci-dedly steeper than it predicts (individuals showing lack of respectfor family values?)