Uniaxial-Pressure-Induced Release of Magnetic Frustration in a Triangular Lattice Antiferromagnet YbCuGe

Round 1

Reviewer 1 Report

Dear Editor, the paper "Uniaxial-pressure-induced release of magnetic frustration in a triangular lattice antiferromagnet YbCuGe" co-authored by K. Umeo et al. and intended for publication in Metals reports experimental magnetization and specific heat studies on a frustrated antiferromagnetic YbCuGe phase. For these studies authors developed high pressure cells for measurements of physical properties under non-hydrostatic conditions. The main outcome of the work is that application of uniaxial pressure induces release of the magnetic frustration in YbCuGe as a result of structural deformations. These results are of potential interest for scientists studying magnetically frustrated systems. However, the following points should be addressed before considering this paper for publication.

1. Chemical compositions and stoichiometries of the synthesized samples should be confirmed with microscopy techniques. In addition, basic structural characterization should be performed (i.e. powder diffraction at ambient conditions) to confirm crystal structures and phase purity. In addition, authors indicate that "TN depends slightly on the samples" (line 107).
2. Fig. 2 shows a setup for the ac calorimetry measurements under uniaxial pressure. One can see that the In metal used as a pressure gauge is not in the same chamber with the sample but underneath the lower piston. How do authors manage to measure P in this way and how they estimate the pressure accuracy?
3. Fig. 3  d. The graphs for the  0 and 0.33 GPa data overlap. Authors should shift them to see better the corresponding transitions. Tha P = 0.4 GPa data is too noisy to conclude on the temperature of the transition, the error should be large. Authors should estimate the error and add it to Fig. 5.
4. When P is applied parallel to the c axis (Fig. 3c) the susceptibility decreases which suggests that the net value of J decreases. However, it  is expected that Ja decreases while Jc increases, as mentioned in the paper (line 118). Why Ja dominates the Jc?
5. Authors present schematic scenarios of deformations of the crystal lattice (Fig. 5, inset). It would be very useful to do diffraction studies at these conditions and to experimentally retrieve this information. Lack of this information makes authors "guess" about the corresponding magnetic coupling (i.e. line 122 - In this case, the Yb-Yb distance parallel to the pressure decreases but that nonparallel to the pressure in the c plane increases. This makes it difficult to guess how the value of Ja would change). Authors could calculate corresponding coupling constants if experimental structural data were available
6. The core conclusion of the paper is "that TN increases by the application of P only along the  a axis, which violates the symmetry of the triangular lattice. This finding indicates the release of the  frustration inherent in the triangular lattice of Yb ions of this compound." However, no clear data on increase in Tn is present (see the point 3 above). Increase in TN can be only suggested from the specific heat measurements (Fig. 4b). However, how reliable is this conclusion? The absolute changes are rather small, in addition there is a discrepancy between the M and C values for P || C data (Fig. 5). Authors should address this point.
7. The manuscript is too short for an article, it should be rather considered as a communication.

In summary, major revision is necessary prior to considering this manuscript for publication. 

Author Response

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Reviewer 2 Report

This is a well written manuscript that addresses a topic of fundamental importance. The results are clearly presented and the interpretation is sound.

Only a few typos have been detected:

Line 48: Wiess --> Weiss

Line 81: a diamond powder --> diamond powder (remove "a")

 

Author Response

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Reviewer 3 Report

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Comments for author File: Comments.pdf

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