codeigniter An uncaught Exception was encountered Type: RuntimeException not working in Linux server

Am creating a website using codeigniter. All the codes are working in localhost(XAMPP).

But same code not working in Linuxserver showing error like

An uncaught Exception was encountered

Type: RuntimeException

Message: Unable to locate the model you have specified: Admin_user

Filename: /home/capitalw/public_html/domain/system/core/Loader.php

Line Number: 344

Backtrace:

File: /home/capitalw/public_html/domain/application/controllers/Admin.php Line: 10 Function: model

File: /home/capitalw/public_html/domain/index.php Line: 315 Function: require_once

Here my codes are

application/controller/Admin.php

class Admin extends CI_Controller {

    public function __construct(){
        parent::__construct();
        //$this->load->library('common');
        $this->load->library('form_validation');
        $this->load->model('admin_user');

    }
}

application/models/admin_user.php

class Admin_user extends CI_Model {

    function __construct()
    {
        parent::__construct();

    }
//some inser update codes here


}