Defocusing effects in the reflexion technique for the determination of preferred orientation

The defocusing of the diffracted beam in a texture goniometer using the reflection technique for the determination of the preferred orientation is discussed. By means of textureless (random) specimens of the ferromagnetic material Ba₃Co₂Fe₂₄O₄₁ this defocusing is measured for several diffraction planes in two cases: (1) a narrow and (2) a wide receiving slit. Calibration functions to correct for defocusing effects are calculated using an equation given by Gale & Griffiths [Brit. J. Appl. Phys. (1960). 11, 96-102]. The calculated functions plotted versus the angle of specimen tilt are compared with the relative intensities measured on random specimens.