Auto login after registration in CakePHP 1.3

I create a new User with this code: controller:

$this->User->createUser($this->data)

Model:

function createUser(){ 
    $this->create();
}

After that I want to login the user. I already tryed this (in the controller):

$this->Auth->login($this->data);
$this->redirect('home');

Unfortunately it does not work that way. Am I doing something wrong?

For cake1.3

In your controller

$id = $this->User->createUser($this->data);
$this->data['User'] = array_merge($this->data['User'], array('id' => $id));
$this->Auth->login($this->data);
$this->redirect('home');

Model

before creating user you've to hash the user entered password and then save into the database

function createUser($data){ 
    $data['User']['password'] = md5($data['User']['password']);
    $this->save();
    return $this->id; // return id of last saved record
}