The present invention is directed to methods for polishing and cleaning a wafer having CoFeNi structures within alumina fill to achieve corrosion-free, smooth, and planar surface. A preferred chemical mechanical polishing (CMP) method includes a CMP polishing compound including alumina abrasive particulates, 1H-Benzotriazole (BTA), and hydrogen peroxide (H₂O₂). A cleaning solution for CoFeNi structures in alumina fill of the present invention preferably includes 4-Methyl-1H-Benzotriazole in a concentration range of from 1% to 5%, 5-Methyl-1H-Benzotriazole in a concentration range of from 1% to 5%, hydrogenated 4-Methyl-1H-Benzotriazole in a concentration range of from 1% to 5%, hydrogenated 5-Methyl-1H-Benzotriazole in a concentration range of from 1% to 5%, sodium octanoate in a concentration range of from 5% to 10%, and water in a concentration range of from 65% to 95%. The cleaning solution is typically used with DI water to create an applied solution having a range of from 0.1% to 10% by volume of the cleaning solution.