ISSN:
1434-6036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Neutron powder diffraction and magnetization measurements have been performed in stoichiometric Pr2NiO4+δ(δ≈0), which at room temperature (RT) is orthorhombic (Bmab). Ni2+ becomes three dimensionally (3D) antiferromagnetically ordered atT N ≈325K, with a propagation vectork=[100], and spins oriented along thea axis (parallel to the propagation vector). The magnetic structure belongs to theΓ 7g (−−+)-representation (g x mode, Shubnikov groupB pmab') ofBmab, and a magnetic moment of 1.5μ B is measured at 155K. This compound undergoes two different structural phase transitions. First, going down in temperature, Pr2NiO4 transforms by a first order phase transition from orthorhombic (Bmab) to tetragonal (P42/ncm) atT c1≈115K. At high temperature, we can predict a transformation from orthorhombic (Bmab) to tetragonal (I4/mmm) in a continuous way. The extrapolated temperature for this second structural transition isT c2≈1500±100K. The low temperature structural transformation allows a change in the magnetic structure which forT〈T c1 is better described in the orthorhombic symmetry. Just belowT c1 the magnetic structure is described by the:Γ 3g (−+)-representation ofPccn(gxcyfz mode, Shubnikov groupPc′c′n), this magnetic phase begins to disappear going down in temperature and at the same time a new magnetic phase grows. This new magnetic structure is described by theΓ 1g ofPccn (c xgyaz mode, Shubnikov groupPccn). Both magnetic structures coexist in a certain temperature range. At 1.5 K thec xgyaz mode represents the total of the magnetic ordering. To reproduce the observed magnetic intensities we are forced to consider that Pr3+ is polarized below 40 K, with a magnetic structure which is coupled to the Ni sublattices (i.e.Γ 1g andΓ 3g ). The magnetic moment at low temperature for Pr is about 1.28μ B .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01324337
