Antiferromagnetic phase transition in garnet-type AgCa2Mn2V3O12 and NaPb2Mn2V3O12 Original Research Article

Ferrimagnetism has been extensively studied in garnets, whereas it is rare to find the antiferromagnet. Present work will demonstrate antiferromagnetism in the two Mn–V-garnets. Antiferromagnetic phase transition in AgCa2Mn2V3O12 and NaPb2Mn2V3O12 has been found, where the magnetic Mn2+ ions locate only on octahedral A site. The heat capacity shows sharp peak due to antiferromagnetic order with the Néel temperature TN=23.8 K for AgCa2Mn2V3O12 and TN=14.2 K for NaPb2Mn2V3O12. The magnetic entropy change over a temperature range 0–50 K is 13.9 J K−1 mol-Mn2+-ions−1 for AgCa2Mn2V3O12 and 13.6 J K−1 mol-Mn2+-ions−1 for NaPb2Mn2V3O12, which are in good agreement with calculated value of Mn2+ ion with spin S=5/2. The magnetic susceptibility shows the Curie–Weiss behavior over the range 29–350 K. The effective magnetic moment μeff and the Weiss constant θ are μeff=6.20 μB Mn2+-ion−1 and θ=−34.1 K (antiferromagnetic sign) for AgCa2Mn2V3O12 and μeff=6.02 μB Mn2+-ion−1 and θ=−20.8 K for NaPb2Mn2V3O12.