How do I set the Created By when I create a new record via custom button?

I have a custom button that allows users to create a new record in another module. When they do this, it says the Created By is me. I have tried sending the Created_By value in the map, but it does not seem to be working. What I am doing wrong?

mp = Map();

userResp = zoho.crm.getRecords("users",1,200,{"type":"ActiveUsers"});
users = userResp.getJSON("users");
user = users.getJSON("user");

currentUserEmail = zoho.loginuserid;

currentUserId = "";

for each user in users
{
    userEmail = user.get("email");
    userId = user.get("id");
    if(userEmail == currentUserEmail )
    {
        currentUserId = userId;
    }
}

mp.put("Created_By",currentUserId);

createResp = zoho.crm.createRecord("Samples1",mp);