Relative amplitude q of the variation of the mean magnetic field modulus against the ratio r of the extrema of the mean longitudinal field (see text). Dots identify values of q computed from the ⟨ B ⟩ data of this paper and of Paper I; triangles are used for field moduli from the literature. Filled symbols correspond to stars for which the ⟨ B_z ⟩ measurements are based on CASPEC observations (this paper; Mathys 1994; Mathys & Hubrig 1997), open symbols to other good ⟨ B_z ⟩ measurements from the literature (references given in the text). The dashed diagonal line, q = (3−r)/2, emphasises the concentration of the majority of the stars of the sample in the lower left part of the figure: namely, high amplitudes of variation of ⟨ B ⟩ are observed when both the positive and negative magnetic poles of the star come into sight during its rotation cycle.