Antiferromagnetic phase transition in garnet-type AgCa2Mn2V3O12 and NaPb2Mn2V3O12

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.

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► Ferromagnetism has been extensively studied in garnets so far.
► Antiferromagnetism in twoV-garnets AgCa2Mn2V3O12 and NaPb2Mn2V3O12 has been found.
► Néel temperature is 23.8 K for AgCa2Mn2V3O12 and 14.2 K for NaPb2Mn2V3O12.
► Details of thermal and magnetic properties have been reported.