A special type of 180° wall has been observed in (111) wafers of Y 3 Fe 5− t Ga t O 12 [1] with M⇒ normal to the wafer plane where the Ga content varied laterally by Δ t /Δ x = 0.02 mm −1 . This Ga gradient gave rise to a line of magnetic compensation extending across the platelet where t ≈ 1.3 . Applying a magnetic field this new wall which we further call ‘compensation wall’ generates along the compensation line [2]. The wall is characterized by essentially three properties: (1) It is fixed by an applied field to a compensation line; (2) its wall energy and wall thickness depend on the applied field; (3) it moves with changing temperature. The compensation wall separates domains of different sublattice orientations, but equal direction of the total magnetization M⇒(r⇒), since M⇒(r⇒) aligns parallel to the applied field. With increasing field strength the wall expands, while its center line stays fixed. A small temperature variation results in a considerable displacement of the compensation line and, consequently, the compensation wall (Fig. 1) due to the different temperature dependence of the sublattice magnetizations. The structure of this wall is studied by means of magnetooptic measurement [3, 4].