title: Structure-Property Relationships in α-, β'-, and γ-Modifications of Mn3(PO4)2.
abstract: The manganese orthophosphate, Mn3(PO4)2, is characterized by the rich variety of polymorphous modifications, α-, β'-, and γ-phases, crystallized in monoclinic P21/c (P21/n) space group type with unit cell volume ratios of 2:6:1. The crystal structures of these phases are constituted by three-dimensional framework of corner- and edge-sharing [MnO5] and [MnO6] polyhedra strengthened by [PO4] tetrahedra. All compounds experience long-range antiferromagnetic order at Neel temperature TN= 21.9 K (α-phase), 12.3 K (β'-phase), and 13.3 K (γ-phase). Additionally, second magnetic phase transition takes place at T* = 10.3 K in β'-phase. The magnetization curves of α- and β'-modifications evidence spin-floplike features at B = 1.9 and 3.7 T, while the γ-Mn3(PO4)2stands out for an extended one-third magnetization plateau stabilized in the range of magnetic field B = 7.5-23.5 T. The first-principles calculations define the main paths of superexchange interaction between Mn spins in these polymorphs. The spin model for α-phase is found to be characterized by collection of uniform and alternating chains, which are coupled in all three directions. The strongest magnetic exchange interaction in γ-phase emphasizes the trimer units, which make chains that are in turn weakly coupled to each other. The spin model of β'-phase turns out to be more complex compared to α- or γ-phase. It shows complex chain structures involving exchange interactions between Mn2 (Mn2', Mn2″) and Mn3 (Mn3', Mn3″). These chains interact through exchanges involving Mn1 (Mn1', Mn1″) spins.
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.|National University of Science and Technology , Moscow 119049, Russia.|Ural Federal University , Ekaterinburg 620002, Russia.
authors.forename: Olga S
authors.initials: OS
authors.lastname: Volkova
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.|National University of Science and Technology , Moscow 119049, Russia.
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Shvanskaya
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.
authors.forename: Evgeny A
authors.initials: EA
authors.lastname: Ovchenkov
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Zvereva
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.
authors.forename: Anatoly S
authors.initials: AS
authors.lastname: Volkov
authors.affiliation: Ural Federal University , Ekaterinburg 620002, Russia.|Institute of Experimental Mineralogy, RAS , Chernogolovka 142432, Russia.|Institute of Geology and Petroleum Technologies, Kazan Federal University , Kazan 42008, Russia.
authors.forename: Dmitriy A
authors.initials: DA
authors.lastname: Chareev
authors.affiliation: Aliah University , Kolkata 700156, India.
authors.forename: Kaimujjaman
authors.initials: K
authors.lastname: Molla
authors.affiliation: Aliah University , Kolkata 700156, India.
authors.forename: Badiur
authors.initials: B
authors.lastname: Rahaman
authors.affiliation: S. N. Bose National Centre for Basic Sciences , 700098 Kolkata, India.
authors.forename: Tanusri
authors.initials: T
authors.lastname: Saha-Dasgupta
authors.affiliation: M. V. Lomonosov Moscow State University , Moscow 119991, Russia.|National University of Science and Technology , Moscow 119049, Russia.|Ural Federal University , Ekaterinburg 620002, Russia.
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Vasiliev