Magnetic order in the two-dimensional metal-organic framework manganese pyrazinecarboxylate with Mn-Mn dimers

S. Calder, R. Baral, N. Narayanan, and L. D. Sanjeewa

Phys. Rev. Materials 7, 124408 – Published 15 December 2023

Abstract

The magnetic properties of [Mn(pyrazinecarboxylate) $_{2}]_{n}$ , empirical formula $C_{10} H_{6} {MnN}_{4} O_{4}$ , are investigated through susceptibility, heat capacity, and neutron scattering measurements. The structure consists of Mn-Mn dimers linked on a distorted 2D hexagonal structure. The weak out-of-plane interactions create a quasi-2D magnetic material within the larger three-dimensional metal-organic framework structure. We show that this material undergoes a two-stage magnetic transition, related to the low dimensionality of the Mn lattice. First, at 5 K, which is assigned to the initial development of short-range order in the 2D layers. This is followed by long-range order at 3.3 K. Applied field measurements reveal the potential to induce magnetic transitions in moderately small fields of $\sim 2$ T. Neutron powder diffraction enabled the determination of a unique magnetic space group ${P 2_{1}}^{'} / c$ (No. 14.77) at 1.5 K. This magnetic structure consists of antiferromagnetically coupled Mn-Mn dimers with spins principally along the out-of-plane $a$ axis.

Received 29 September 2023
Revised 8 November 2023
Accepted 28 November 2023

DOI:https://doi.org/10.1103/PhysRevMaterials.7.124408

Physics Subject Headings (PhySH)

Magnetic order Magnetism

Neutron diffraction

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

S. Calder ^1,*, R. Baral ¹, N. Narayanan², and L. D. Sanjeewa^2,3

¹Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²University of Missouri Research Reactor (MURR), University of Missouri, Columbia, Missouri 65211, USA
³Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA

^*caldersa@ornl.gov

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 7, Iss. 12 — December 2023

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Rietveld refinement of neutron powder diffraction data for Mn(2-pzc) $_{2}$ collected on the HB-2A instrument with a wavelength of 1.54 $Å$ at 20 K. (b) Crystal structure of Mn(2-pzc) $_{2}$ . The box represents the unit cell in the $P 2_{1} / c$ space group. (c) Nearest- and next-nearest-neighbor Mn ions are bonded through distinct pathways of Mn-O-Mn and Mn-O-C-O-Mn.
Reuse & Permissions
Figure 2
(a) View of the 2D layers in Mn(2-pzc) $_{2}$ . (b) The nearest-neighbor dimers (thick red line) and next-nearest-neighbor (thin blue line) interactions within the 2D layers are shown between the Mn ions (purple sphere). The Mn ions form a distorted 2D honeycomb structure. The crystallographic unit cell is indicated by the grey box.
Reuse & Permissions
Figure 3
(a) Magnetic susceptibility measurements from 2 K to 300 K. The solid black line is a fit using the Curie-Weiss law. (b) Directional dependent measurements showing a broad anomaly centered around 5 K. Green/yellow are in-plane and blue is out of plane. Measurements were in a 10 kOe field for all three directions. Inset: Out-of-plane magnetic field dependence. (c) Isothermal magnetization measurements for a field applied out of plane. Inset: Directional-dependent measurements at 2 K, where green/yellow are in plane and blue is out of plane. (d) Derivative of the susceptibility reveals two anomalies at 5 K and 3.2 K in a field of 10 kOe out of the plane.
Reuse & Permissions
Figure 4
(a) Zero-field heat capacity measurements on Mn(2-pzc) $_{2}$ from 2 to 200 K. (b) Low-temperature and field-dependent heat-capacity measurements. The magnetic field was applied along the out-of-plane direction.
Reuse & Permissions
Figure 5
(a) Neutron powder diffraction data collected at 1.5 K and 20 K. Inset: Intensity at $Q = 0.65 Å$ as a function of temperature through the magnetic transition. (b) Difference of intensity at 1.5 K and 20 K in the powder diffraction data.
Reuse & Permissions
Figure 6
Refinement of neutron powder diffraction data with $λ = 2.41 Å$ collected at 1.5 K using the magnetic space group ${P 2_{1}}^{'} / c$ with (a) moments along all ( $m_{a}, m_{b}, m_{c}$ ) directions, (inset) magnetic structure, and (b) moments only along $m_{a}$ (inset) magnetic structure. The moments are shown as red arrows on the Mn ions, the nearest-neighbor dimer bonds are blue and the next-nearest-neighbor bonds are the dashed lines. The grey box represents the magnetic unit cell. (c) View of the 2D layers along the $a$ axis. The red/black circles correspond to up/down spin directions on the Mn ion.
Reuse & Permissions

Physical Review Materials