Magnetoresistive effect element and method of manufacturing the same

A magnetoresistive-effect element comprising:

• a first ferromagnet;
• a first layer on the first ferromagnet, the first layer comprising magnesium oxide;
• a second ferromagnet on the first layer;
• a metal layer above the second ferromagnet;
• and
• a second layer on the metal layer,
• wherein:
• the second layer and the magnesium oxide have a selected ratio larger than 1 to etching by ion beams, and
• the second layer comprises at least one of silver sulfate (I), an aluminum chloride, aluminum fluoride, mullite, aluminum sulfate, an arsenic pentoxide, arsenic trioxide, an aluminum oxide, a witherite, barium fluoride, barium nitrate, alexandrite, calcium hydroxide, a calcium chloride, calcite, fluorite, dolomite, a calcium oxide, perovskite, malachite, a fayalite, lanthanum oxide, magnesium hydroxide, a forsterite, spinel, magnesite, a cryolite, a beta2-tridiymite, samarium oxide, and rutile.