$('title').text() Don't work in IE

$('title').text() Don't work in IE

I want to change the page title using jQuery, But it doesn't work in IE, Why?
The code like this:
alert( $('title').text() ); // empty in IE
$('title').text('Some Text!'); // Don't work in IE
Yes, we can use "document.title = 'xxxx';" to change the title conent.