Javascript runtime error json is undefined

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C#

Javascript

jQuery

MVC6

I am new in MVC,I have created forgot password screen,
I want to fetch EmailId from Username entered in Username textbox by user.

But i am getting error Javascript runtime error Json is undefined

What I have tried:

<script src="/Scripts/json2.js"></script>
<script src="/Scripts/jquery-1.10.2.js"></script>
<script type="text/javascript">
    $(document).ready(function(){
        $("#UserName").change(function () {
            $.ajax({
                Type:"GET/POST",
                ContentType:"application/json;charset=utf-8",
                url:'/Login/GetEmail?UserId=0&IsEnabled=False&RoleId=0&Status=False',
                data:{allData : Json.Stringify(Model)},
                dataType:"json",
                success: function(data){
                    //alert(data.property1 + data.property2 );
                    if (data == null) {
                        alert('User Id not available')
                    }
                    else if (data.EmailId == null || data.EmailId == "") {
                        alert('Email Id not available');
                    }
                    else {
                        $("#EmailId").val("");
                    }
                },
                error: function(){
                    alert("Error");
                }
            });
        });
    });
</script>

Action in controller

public User GetEmail(User u)
{
    List<User> uList = gc.Users.Include(p => p.Role).Where(p => p.UserName == u.UserName).ToList();
    return u;
}