Hello nixnet,
You're looking for functionality of the response object. Check out:
Zend Framework: Documentation
Your probably looking for something like:
$this->getResponse()->setBody('content', $this->view->render('login/index.phtml'));
Additionally, the front controller will always try to render the corresponding .phtml file for the controller unless you tell the front controller not to, with something like:
$front->setParam('noViewRenderer', true);
Side effect of this is that you will always have to render the view. The alternative, of course, is to just have a blank corresponding .phtml file.
Hope this helps.
steve