radtools.MagnonDispersion.A

method

MagnonDispersion.A(k)

Computes A(k) matrix.

\[A(\boldsymbol{k})^{ij} = \dfrac{\sqrt{S_i\cdot S_j}}{2}\boldsymbol{u}^T_i\boldsymbol{J}_{i,j}(-\boldsymbol{k})\overline{\boldsymbol{u}}_j\]

where indices \(i\) and \(j\) correspond to the atoms in the exchange pair.

Parameters:

k(3,) array-like

Reciprocal vector. In absolute coordinates.