A person who is a competent adult may, as principal, designate another person or an authorized corporation as the person’s attorney-in-fact by a written power of attorney. The power of attorney is validly executed when it is dated and signed by the principal and, in the case of a signature on behalf of the principal, by another, or by a mark, acknowledged by a notary public. Only powers of attorney validly created pursuant to this section or section 523.02 are validly executed powers of attorney for the purposes of sections 523.01 to 523.24.