Pengaruh Dopan Ag terhadap Resistivitas dan Sifat Kemagnetan Bahan La1,4Ca1,6-xAgxMn2O7 (x=0; 0,4; 0,5; 0,6) dengan Metode Sintesa Sol Gel = The Effect of Ag-Doping on Resistivity and Magnetic Properties La1,4Ca1,6-xAgxMn2O7 (x=0; 0,4; 0,5; 0,6) Materials with Sol Gel Synthesis Methode.