Magnetic field induced phase transition in spinel ${\mathrm{GeNi}}_{2}{\mathrm{O}}_{4}$

Magnetic field induced phase transition in spinel ${GeNi}_{2} O_{4}$

T. Basu, T. Zou, Z. Dun, C. Q. Xu, C. R. Dela Cruz, Tao Hong, H. B. Cao, K. M. Taddei, H. D. Zhou, and X. Ke

Phys. Rev. B 102, 134421 – Published 15 October 2020

Abstract

Cubic spinel ${GeNi}_{2} O_{4}$ exhibits intriguing magnetic properties with two successive antiferromagnetic phase transitions $(T_{N 1} \approx 12.1$ and $T_{N 2} \approx 11.4 K)$ with the absence of any structural transition. We have performed detailed heat-capacity and magnetic measurements in different crystallographic orientations. A magnetic phase in the presence of the magnetic field $(H \geq 4 T)$ along the [111] direction is revealed, which is not observed when the magnetic field is applied along the [100] and [110] directions. High-field neutron powder-diffraction measurements confirm such a change in the magnetic phase, which could be ascribed to a spin reorientation in the presence of the magnetic field. A strong magnetic anisotropy and competing magnetic interactions play a crucial role in the complex magnetic behavior in this cubic system.

Received 17 February 2020
Accepted 24 September 2020

DOI:https://doi.org/10.1103/PhysRevB.102.134421

Physics Subject Headings (PhySH)

Frustrated magnetism Magnetic anisotropy Magnetic phase transitions

Spinels

Neutron scattering Specific heat measurements Susceptibility measurements

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

T. Basu ¹, T. Zou¹, Z. Dun², C. Q. Xu¹, C. R. Dela Cruz³, Tao Hong³, H. B. Cao ³, K. M. Taddei³, H. D. Zhou ², and X. Ke¹

¹Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
²Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
³Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

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Vol. 102, Iss. 13 — 1 October 2020

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Figure 1
(a) The main panel displays the temperature variation of heat capacity of single-crystal ${GeNi}_{2} O_{4}$ measured under zero magnetic field and with 9 T magnetic field applied along the [111] crystallographic axis. The inset shows heat-capacity measurement acquired on polycrystalline ${GeNi}_{2} O_{4}$ samples. (b) Magnetic susceptibility of single-crystal ${GeNi}_{2} O_{4}$ measured with 0.1 and 9 T magnetic field applied along the [111] axis, respectively. (c) Temperature dependence of heat capacity of single-crystal ${GeNi}_{2} O_{4}$ with various fields applied along the [111] axis. The absolute value along $y$ axis is slightly shifted to get a better visualization of peak shifting for different field. (d) Temperature dependence of heat capacity of single crystal ${GeNi}_{2} O_{4}$ with 9 T magnetic field applied along the [100], [110], and [111] axes, respectively.
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Figure 2
Isothermal magnetization at selective temperature of ${GeNi}_{2} O_{4}$ single crystal when magnetic field is applied along the [111] crystallographic axis.
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Figure 3
Powder neutron-diffraction pattern of ${GeNi}_{2} O_{4}$ collected at 2 and 25 K under zero field. The black and green symbols represent the experimental data, while the red solid line shows the Rietveld fitting for 2-K neutron data. The vertical bars display the Bragg peak positions. The upper vertical lines represent Bragg peaks of crystal structure ${GeNi}_{2} O_{4}$ , the middle vertical lines represents Bragg peaks of Al sample, the lower vertical line represents magnetic Bragg peaks of ${GeNi}_{2} O_{4}$ . The magenta curve shows the difference between the experimental and calculated intensity for 2-K data. (b) Peak intensity of (1/2 1/2 1/2) and (3/2 1/2 1/2) magnetic Bragg peaks as function of temperature under zero field. (c),(d) best fit of Rietveld refinement of single-crystal data at 4.7 and 11.6 K, respectively.
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Figure 4
Possible spin structures (a)–(c) at 4.7 K (below $T_{N 2}$ ) and (d) 11.6 K (below $T_{N 1}$ ) in the absence of applied magnetic field, as described in the text.
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Figure 5
(a) Powder neutron diffraction of ${GeNi}_{2} O_{4}$ collected at 2 K under $H = 0$ and 6 T magnetic field. (b) Peak intensity of (1/2 1/2 1/2) and (3/2 1/2 1/2) magnetic Bragg peaks as a function of temperature under 6 T magnetic field. (c),(d) Magnetic field dependence of neutron-scattering intensity at 2 K of (1/2 1/2 1/2) and (3/2 1/2 1/2) Bragg peaks respectively, in warming (open symbol) and cooling (closed symbol) of field condition.
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Figure 6
T-H phase diagram with the magnetic field applied along the [111] crystalline orientation to visualize the change in magnetic structure as a function of T and H.
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Physical Review B

covering condensed matter and materials physics

Magnetic field induced phase transition in spinel ${GeNi}_{2} O_{4}$

T. Basu, T. Zou, Z. Dun, C. Q. Xu, C. R. Dela Cruz, Tao Hong, H. B. Cao, K. M. Taddei, H. D. Zhou, and X. Ke

Phys. Rev. B 102, 134421 – Published 15 October 2020

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Physical Review B

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Magnetic field induced phase transition in spinel GeNi2O4

T. Basu, T. Zou, Z. Dun, C. Q. Xu, C. R. Dela Cruz, Tao Hong, H. B. Cao, K. M. Taddei, H. D. Zhou, and X. Ke

Phys. Rev. B 102, 134421 – Published 15 October 2020

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Magnetic field induced phase transition in spinel ${GeNi}_{2} O_{4}$