How to resolve null return in Laravel query?

Given my Models Person and Student. Now, one of my controller is doing this:

$person_id = AppModelsPerson::insertGetId(['name' => $request->name, ...]);
AppModelsStudent::create(['person_id' => $person_id, ...]);
$student = AppModelsStudent::where('person_id', $person_id)->first();
dd($student);

During execution, everything has been save but My problem is why i am receiving null on die and dump?

By the way, my student tables’ primary and foreign key is the person_id column.

Edit

class Student extends Model
{
    protected $fillable = ['section', 'current_year'];//there are other attribute here which I didn't show because I am using mobile

    public function person(){
       return $this->belongsTo('AppModelsPerson', 'person_id', 'id');
    }

    ...
}

Answer

Add person_id in $fillable property:

protected $fillable = ['section', 'current_year', 'person_id'];