Multilayer body, element including the multilayer body, and method of producing the multilayer body

An element comprising:

• a piezoelectric layer made of a crystal of an oxide having piezoelectricity;
• a metal layer;
• and
• a magnetic layer made of a crystal of a Heusler alloy that is a ferromagnetic material,
• wherein
• the piezoelectric layer, the metal layer, and the magnetic layer are stacked in this order,
• the metal layer has
• a thickness of 10 nm or more and 40 nm or less, and
• an average content of oxygen of 5 at % or less, and
• the piezoelectric layer has an average content of a metal element constituting the metal layer of 5 at % or less, within a range of 10 nm from an interface with the metal layer.

A method of producing a multilayer body comprising:

• a metal layer formation process in which a metal layer is formed on or above a piezoelectric layer made of a crystal of an oxide having piezoelectricity;
• and
• a magnetic layer formation process in which a magnetic layer made of a crystal of a Heusler alloy that is a ferromagnetic material is formed on or above the metal layer,
• wherein in the magnetic layer formation process,
• by molecular beam epitaxy,
• the magnetic layer is formed at a growth temperature of 80° C. or more and 450° C. or less.