Abstract: A magnetic field sensor element with a piezo electric substrate having predetermined shear wave velocity VS, two pairs of interdigital electrodes, arranged on the substrate on the ends of a delay section, having a period length p of at least 10 micrometers, a non-magnetic, electrically non-conductive guide layer arranged on the substrate along the delay section, and a magnetostrictive functional layer arranged on the guide layer, wherein the shear wave velocity in the guide layer is smaller than VS, wherein a) the substrate is oriented to generate and propagate mechanical shear waves upon applying a temporally periodic, electrical voltage to at least one interdigital electrode pair in the range of frequency VS/p and, wherein b) the thickness of the guide layer equals at least 10% and at most 30% of the period length p of the interdigital electrodes.