Magnetic unit cells

Furthennore, the magnetic diffraction and the nuclear diffraction do not interfere with one another, and the nuclear and magnetic intensities simply add together, although in many cases the magnetic unit cell is larger than the nuclear unit cell, which produces additional diffraction peaks. 

Fig. 12-5. The Magnetic Unit Cell of MnFa Showing the Spin Orientation of the Magnetic Ions. The fourfold axis is in the direction of the spin vectors. The nonmagnetic ions are not shown.

Magnetic symmetry associated with the group P62m, 757 Magnetic unit cell of MnF2,754 Malkin, I. G, 349... 

FIGURE 2.14 The magnetic ordering in NiO. The Ni planes only are pictured, and alternate close-packed layers have opposing magnetic moments. Note that the magnetic unit cell length is double that of the normal unit cell. 

FIGURE 9.9 Magnetic unit cell of NiO with the crystallographic or chemical unit cell indicated. 

Fig.l. Stripe models for 1/3 doping.18 Arrows indicate correlated Ni magnetic moments circles indicate oxygen sites filled circles indicate locations of doped holes on oxygen sites. Bold dashed lines indicate positions of domain walls, while bold solid lines outline a magnetic unit cell. The two-magnon Raman process is shown also bold arrows demonstrate spins on adjacent sites and curved lines indicate broken magnetic bonds. 

Combination of ordering of first and third kind. Magnetic unit cell is triple the chemical unit cell in [010] (magnetic [001]) direction. 

Figure 64 A possible magnetic structure for k-Mn02 with 128 spins per magnetic unit cell. The open and closed circles represent spins of opposite direction. (Reprinted with permission from Ref 136, 1998 American Chemical Society)...

The sum is over the magnetic ions in the magnetic unit cell. The /th ion has effective spin form factor fj(x) and Debye-Waller factor exp[—... 

Figure 3.3 Magnetic structure of Ho2BaNi05, space group Immm. There are only three magnetic atoms per primitive unit cell. Ni at (0, 0, 0) and Ho at positions 1(1/2, 0, z), 2( 1/2, 0, z) with z = 0.2025. The propagation vector is k = (1/2,0,1/2). The magnetic moments are not in scale, the amplitude of those of Ho atoms have been arbitrarily multiplied by 0.3 for representation purposes. The magnetic unit cell doubled along a and c. The magnetic moments of the three atoms are Ni(w, 0, w), with u 0.59 [Ib, w 1.3 Pb, Ho1(/7, 0, q), Ho2(/ , 0, q), with 0.1 Pb and q 9[Ib (ref. 17).

Nuclear unit cell Magnetic unit cell... 

Figure 5.25 Nuclear and magnetic unit cell for nickel oxide...

Apart from the disordered noncollinear spin structures there are also ordered ones. A prominent example of these is the transition-metal compound y-FeMn, which has a magnetic unit cell that is not much larger than the chemical one. On the other hand, magnetic spiral structures, which are quite common in rare earth metals, can possess very large or even infinite magnetic unit cells. 

The antiferromagnetic ordering below was proved by Cox et al. (1986). They found a simple arrangement of the U moments of (0.8 0.1 )/r n (at 5 K). These are oriented antiparallel to their nearest-neighbours within the basal planes and to the near-neighbours along the c-axis. The magnetic unit cell is identical with the chemical unit cell. 

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