从外部库文件codeigniter访问控制器

I have added a external library controller in "application/libraries/Validate_login.php".

When i load a controller in application/controllers/ from external library controller, i'm getting error Library verifylogin Not Found.

Validate_login.php

class Validate_login extends CI_Controller {
      function __construct()
       {
         parent::__construct();
         $this->load->model('loginuser');
         $this->load->helper('url');
         $this->load->library('verifylogin');// controller which is in application/controllers/
       } }

$this->load->library('verifylogin');// controller which is in application/controllers/

$this->load->library() will load libraries within the "application/libraries" directory. That's why it cannot be found.