stores 3x3 matrices for using them in the Hailtonian

Sub fields

mat
Stores the actual values of 3x3 matrices, in a matrix with dimensions of , if assigned for a bond, the unit of energy is stored in spinw.unit (default value is meV).
color
Color assigned for every matrix, stored in a matrix with dimensions of , with each column defining an RGB value.
label
Label for every matrix, stored as string in a cell with dimensions of .