Texts that an author has himself written are his own intellectual property.
To refer to a text as someone's "intellectual property" spreads a dangerous propaganda term which also spreads confusion. (See http://www.gnu.org/philosophy/words-to-avoid.html for more explanation of why this is so.) The text is still the author's "intellectual property," in the sense that authorship is retained by the author, and the text may not be plagiarized by anyone, That is even more confusing, since it stretches the meaning of "intellectual property" even further than normal. To avoid confusion, I suggest you rewrite it as follows: When you write an article, you are the copyright holder; you are free to give away or sell copies, on-paper or on-line (e.g., by self-archiving), as you see fit.